Term
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Definition
-Augustinian monk who discovered basic principles of heredity through his experiments with garden peas. He studied approximately 30,000 pea plants in the development of his theory.
-Received no recognition for his work during his lifetime |
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Term
Unit inheritance
Segregation
Independent assortment |
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Definition
| Gregor Mendel derived three laws from his experiments: |
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Term
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Definition
| parental phenotypes do not blend in offspring |
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Term
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Definition
| two members of a pair of genes segregate and pass to different gametes |
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Term
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Definition
| random recombination of maternal and paternal chromosomes in gametes. |
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Term
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Definition
Also known as single gene inheritance
Describes a trait that is attributable to a single gene |
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Term
Autosomal dominant
Autosomal recessive
X linked recessive
X linked dominant |
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Definition
| 4 Patterns of Mendelian Inheritance |
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Term
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Definition
| A gene, which is expressed even when present in only one copy, is |
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Term
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Definition
| A gene expressed only when two copies are present is |
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Term
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Definition
| In a male with an ___ disorder, only one copy of a gene is needed to produce the disease. |
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Term
Marfan's-- autosomal recessive
Sickle cell anemia-- autosomal recessive
Color blindness-- x linked recessive |
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Definition
| Examples of Single Gene Disorders |
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Term
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Definition
| Most disorders caused by enzyme defects are |
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Term
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Definition
| Disorders caused by non-enzymatic or structural proteins are usually |
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Term
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Definition
| Entire chromosomes are missing, duplicated, or otherwise altered. Down Syndrome, Turner Syndrome |
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Term
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Definition
| Single genes are altered. Also known as Mendelian disorders. Cystic fibrosis, Sickle Cell Disease |
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Term
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Definition
| result from a combination of genetic and environmental causes. Cleft lip, cleft palate, diabetes |
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Term
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Definition
| relatively small number of disorders (approximately 70) caused by alterations in the mitochondrial chromosome |
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Term
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Definition
| Refers to the different forms, or DNA sequences, that a gene may have in a population |
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Term
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Definition
| condition in which the number of chromosomes is not a multiple of 23, as in trisomy, and monosomy |
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Term
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Definition
| The 22 pairs of chromosomes excluding the sex chromosomes X and Y |
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Term
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Definition
| region of a chromosome that separates the two arms; centromeres are the sites of attachment of spindle fibers during cell division |
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Term
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Definition
| The combination of proteins and nucleic acids that makes up chromosomes |
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Term
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Definition
| Threadlike structure (colored body) consisting of chromatin. Genes are arranged along this structure |
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Term
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Definition
| a group of three mRNA bases, each of which specifies an amino acid when translated. |
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Term
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Definition
| Having two copies of each chromosome. In humans, the number is 46 |
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Term
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Definition
| Allele that is expressed in the same way in a single copy (heterozygotes) as in a double copy (homozygotes) |
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Term
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Definition
| organisms whose cells have true nuclei |
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Term
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Definition
| the fundamental unit of heredity. A specific region of a chromosome that codes for a single polypeptide (linear chain of amino acids). |
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Term
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Definition
| the combinations of mRNA codons that specify individual amino acids |
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Term
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Definition
| the totality of an organism’s DNA |
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Term
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Definition
| An individual’s allelic constitution at a locus. The precise allelic composition (i.e., letters in the genetic code) with respect to a particular gene |
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Term
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Definition
| a combination of alleles (for different genes) that are located closely together on the same chromosome and that tend to be inherited together |
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Term
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Definition
| cells responsible for the production of gametes |
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Term
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Definition
| refers to cells that have one copy of each chromosome, the typical state for gametes. In humans, the number is 23 |
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Term
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Definition
| Refers to a gene that is present in only a single copy. Most commonly, refers to genes on the single male X chromosome, but can refer to other genes in the haploid state, such as the genes homologous to a deleted region of a chromosome |
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Term
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Definition
| an individual who has two different alleles at a locus |
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Term
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Definition
| the protein core around which DNA is wound in a chromosome |
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Term
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Definition
| an individual in whom the two alleles at a locus are the same |
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Term
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Definition
| a display of chromosomes ordered according to length |
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Term
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Definition
| the chromosome location of a specific gene |
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Term
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Definition
| Cell division in which haploid gametes are formed from diploid germ cells |
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Term
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Definition
| cell division process in which two identical progeny cells are produced from a single parent cell |
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Term
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Definition
| a basic unit of DNA or RNA consisting of one deoxyribose (or ribose in the case of RNA) one phosphate group, and one nitrogenous base. |
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Term
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Definition
| the observed characteristics of an individual produced by the interaction of genes and environment |
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Term
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Definition
| describes genes that have multiple phenotypic effects |
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Term
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Definition
| cell produced during oogenesis that has a nucleus but very little cytoplasm |
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Term
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Definition
| Describes a trait caused by the combined additive effects of multiple genes |
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Term
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Definition
| chromosome abnormality in which the number of chromosomes in a cell a multiple of 23 but is greater than the diploid number |
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Term
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Definition
| a table specifying the genotypes that can arise from the gametes contributed by a mating pair of individuals |
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Term
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Definition
| the two DNA (also RNA) bases, adenine and guanine, that consist of double carbon nitrogen rings. |
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Term
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Definition
| the bases (cytosine and thymine in DNA; cytosine and uracil in RNA) that consist of a single carbon-nitrogen ring |
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Term
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Definition
| an allele that is phenotypically expressed only in the homozygous or hemizygous state |
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Term
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Definition
| a single stranded molecule that consists of a sugar (ribose), a phosphate group, and a series of bases (adenine, cytosine, guanine, and uracil). There are three basic types: messenger, ribosomal, and transfer |
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Term
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Definition
| the process in which an mRNA sequence is synthesized from a DNA template |
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Term
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Definition
| the process in which an amino acid sequence is assembled according to the pattern specified by the mature mRNA transcript |
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Term
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Definition
| Inheritance is based on DNA: the sequence of ____ encodes all instructions needed to build and maintain an organism |
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Term
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Definition
| A ___ is a single DNA molecule together with other molecules (proteins and RNA) needed to support and read the DNA |
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Term
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Definition
| are composed of one or more polypeptides, plus in some cases other small helper molecules (co-factors). they do most of the work of the cell |
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Term
First, an RNA copy of a single gene is made (transcription).
Then, the nucleotide sequence of the RNA copy (messenger RNA) is translated into the amino acid sequence of the polypeptide |
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Definition
| Genes are expressed in a 2 step process: |
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Term
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Definition
| Genes often have several _____: the same gene in the same chromosomal location, but with minor nucleotide changes that yield slightly different proteins |
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Term
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Definition
| having 2 copies of each gene and each chromosome |
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Term
centromere
telomere
origins of replication
pseudogenes
transposable elements
genes that make small RNA's and not proteins |
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Definition
| Chromosomal DNA contains other things besides genes, what are they? |
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Term
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Definition
| where the mitotic spindle attaches |
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Term
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Definition
| special structures on the ends of chromosomes |
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Term
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Definition
| where copying of DNA starts |
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Term
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Definition
| non-functional, mutated copies of genes |
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Term
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Definition
| The basic physical unit of heredity. A linear sequence of nucleotides along a segment of DNA that provides the coded instructions for the synthesis of RNA |
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Term
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Definition
| Humans have between ____ genes |
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Term
Adenine and guanine
Cytosine and thymine |
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Definition
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Term
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Definition
| First DNA is wound around a ____ protein core to form a ____ |
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Term
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Definition
| Second the nucleosomes form a helical ___ each turn of which includes about six nucleosomes |
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Term
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Definition
| Third the solenoids are organized into ____ |
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Term
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Definition
| DNA replication begins as the weak ____ between base pairs break producing single stranded DNA |
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Term
unwinds the double helix
holds the strands apart |
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Definition
| Multiple enzymes are involved in DNA replication. One enzyme ____ and another _____. DNA polymerase travels along the single strand adding nucleotides to the 3’ end of the new strand |
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Term
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Definition
| DNA Replication always proceeds from the ____ end |
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Term
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Definition
| When referring to the orientation of sequences along a gene, the 5’ direction is termed ____ and the 3’ direction is termed ____ |
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Term
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Definition
| While DNA is formed and replicated in the nucleus, protein synthesis takes place in the |
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Term
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Definition
| The DNA code is transcribed into ____ which then leaves the nucleus to be translated into protein |
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Term
Transcription
messenger RNA (mRNA). |
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Definition
| the process by which an RNA sequence is formed from a DNA template. The type of RNA produced by this process is |
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Term
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Definition
| Transcription of DNA to mRNA. ___ proceeds along the DNA strand in the 3' to 5' direction, assembling a strand of mRNA nucleotides that is complementary to the DNA template strand. |
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Term
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Definition
| Transcription factors contain ____ that allow them to interact with specific DNA sequences. In some cases, they bend DNA so that distant enhancer sequences can interact with target genes |
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Term
nuclear enzymes
functional RNA |
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Definition
| Sections of the primary RNA are removed by ____, and the remaining sections are spliced together to form the ____ that will migrate to the cytoplasm |
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Term
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Definition
| The excised RNA sections are called ___ and the sequences that are left to code for proteins are called ___ |
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Term
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Definition
| Only after ___ is complete, does the mature transcript move out of the nucleus into the cytoplasm |
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Term
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Definition
| A significant feature of the genetic code is that it is _____: virtually all living organisms use the same DNA codes to specify amino acids |
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Term
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Definition
| The process in which mRNA provides a template for the synthesis of a polypeptide |
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Term
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Definition
| In the process of translation, the ___ sequence serves as a template to specify sequences of amino acids. These sequences are assembled by ribosomes |
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Term
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Definition
| ___ sequences are seen only once (or possibly a few times) in the genome. It accounts for about 45% of the genome and includes the protein-coding genes |
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Term
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Definition
| represents only a small fraction of all single-copy DNA, most of which is found in introns or in DNA sequences that lie between genes |
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Term
repetitive DNA
dispersed repetitive DNA and satellite DNA |
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Definition
| The remaining 55% of the genome consists of ____, sequences that are repeated over and over again in the genome, often thousands of times. There are two major classes: |
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Term
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Definition
| are clustered together in certain chromosome locations, where they occur in tandem |
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Term
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Definition
| as the name implies, tend to be scattered singly throughout the genome; they do not occur in tandem |
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Term
| cell division (mitosis and cytokinesis) and interphase |
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Definition
| The cell cycle consists of the alteration of __ and ___. DNA replication and protein synthesis take place during interphase |
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Term
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Definition
| the chromosomes become visible under a light microscope. The two sister chromatids are attached at the centromere. The nuclear membrane begins to disappear and spindle fibers begin to form radiating from two centrioles located on opposite sides of the cell |
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Term
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Definition
The chromosomes reach their most highly condensed state.
Clinical diagnosis of chromosomal disorders is usually based on chromosomes in this phase |
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Term
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Definition
The centromere of each chromosome splits.
At the end of this phase the cell contains 92 separate chromosomes, half lying near one side of the cell and half near the other side of the cell. |
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Term
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Definition
| The final stage of mitosis is characterized by the formation of new nuclear membranes around each of the two sets of 46 chromosomes. The spindle fibers disappear and the chromosomes begin to decondense. Cytokinesis usually occurs after nuclear division. With completion of telophase two diploid daughters cells have been formed. |
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Term
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Definition
Cell division in which haploid gametes are formed from diploid germ cells.
Two cell divisions occur |
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Term
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Definition
| (reduction division stage) two haploid cells are formed from a diploid cell. |
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Term
| second meiosis (equatorial division) |
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Definition
| takes place, during which each haploid cell is replicated |
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Term
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Definition
An alteration in the sequence of DNA
All genetic variation originates from this |
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Term
somatic cells
germline cells |
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Definition
Mutations in ___ can lead to cancer
Mutations in ___ can be transmitted from one generation to another |
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Term
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Definition
| The alleles that are present at a given locus are referred to as the individual’s |
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Term
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Definition
| The human genome is approximately ___ base pairs in length |
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Term
Missense
Nonsense
Frameshift
Promoter
Splice site
Mobile element insertion
Expanded repeats |
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Definition
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Term
Silent substitutions
Non-silent substitution
Missense
Nonsense |
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Definition
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Term
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Definition
| Involves the insertion or deletion of one or more base pairs. Tend to be especially harmful when the number of missing or extra base pairs is not a ___ |
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Term
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Definition
| deletions or insertions tend to be especially harmful when the number of missing or extra base pairs is not a multiple of three. Such insertions can alter all of the downstream codons. This is termed a |
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Term
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Definition
| Often, a frameshift produces a ___ downstream of the mutation causing a truncated polypeptide |
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Term
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Definition
| Alters the regulation of transcription or translation |
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Term
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Definition
| ___ can decrease the affinity of RNA polymerase for a promoter site on the DNA resulting in decreased production of a protein |
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Term
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Definition
| These occur at intron-exon boundaries and alter the splicing signal that is necessary for proper excision of an intron |
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Term
| insertion of mobile elements |
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Definition
| Several types of DNA sequences are capable of propagating copies of them-selves; these copies are then inserted in other locations on chromosomes. Such insertions can cause frameshift mutations |
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Term
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Definition
| The insertion of mobile elements has now been shown to cause isolated cases of ___ and other diseases. |
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Term
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Definition
| Affects tandem repeated DNA sequences that occur within or near certain disease-related sites. The repeat units are usually 3 bp long. Occasionally, the number of repeat units increases dramatically. When this occurs, it can cause genetic disease |
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Term
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Definition
| ___ mutations produce dominant disorders such as Charcot-Marie-Tooth disease and Huntington disease |
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Term
| negative dominant mutation |
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Definition
| Another loss of function mutation is the ____ which results in a protein that is not only nonfunctional but also inhibits the function of the protein produced by the normal allele in the heterozygote. |
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Term
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Definition
| Caused a single missense mutation that effects a substitution of valine for glutamic acid at position 6 of the β-globin polypeptide chain |
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Term
| Spontaneous mutations arise naturally during the course of DNA replication. Induced mutations are caused by outside agents collectively referred to as mutagens. |
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Definition
| Spontaneous vs. induced mutations |
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Term
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Definition
| X-rays and nuclear fallout can eject electrons from atoms. These ions can promote chemical changes that change the DNA bases |
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Term
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Definition
| – does not form ions but can move electrons from inner to outer orbits. UV radiation is an example of this. Can cause the formation of covalent bonds between adjacent pyrimidine bases |
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Term
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Definition
| chemicals that have structures which are similar to the DNA bases. They can be mistakenly substituted for a true DNA base during replication. |
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Term
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Definition
| Other chemical mutagens such as ___ can insert themselves between existing bases |
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Term
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Definition
| ____ because of their size are generally more likely to experience mutations |
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Term
methylated CG dinucleotides
advanced paternal age |
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Definition
| Mutation hot spots, such as ___ also occur. For some single-gene disorders, there is an increase in mutation risk with ____. |
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Term
Protein electrophoresis
Southern Blotting and Restriction Fragment Analysis
DNA Amplification using the Polymerase Chain Reaction |
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Definition
| Types of Detection and Measurement of Gene Variation |
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Term
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Definition
| increased the number of detectable polymorphic systems considerably. This technique makes use of the fact that a single amino acid difference in a protein (the result of a mutation in the corresponding DNA sequence) can cause a slight difference in the electrical charge of the protein |
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Term
| restriction fragment analysis |
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Definition
| An early approach to the detection of genetic variation at the DNA level took advantage of the existence of bacterial enzymes known as restriction endonucleases. These enzymes cleave human DNA at specific sequences |
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Term
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Definition
| To visualize only the fragments corresponding to a specific region of DNA, a probe, consisting of a small piece of single-stranded human DNA (a few kilobases [kb] in length), is constructed using recombinant DNA techniques. The probe is labeled and then exposed to the Southern blot. |
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Term
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Definition
| It can detect insertions or deletions in DNA sequences, which cause specific fragments to become larger or smaller. If a disease-causing mutation alters a specific restriction site, as in the case of sickle cell disease, this technique can be used as a cheap and efficient diagnostic tool. Because most disease-causing mutations do not affect restriction sites, this approach is somewhat limited |
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Term
| restriction fragment length polymorphisms (RFLPs), |
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Definition
| Southern blotting was instrumental in analyzing ____, which are found throughout the human genome as a result of normal DNA sequence variation. These sequence variants were used to localize many important disease-causing genes, including those responsible for cystic fibrosis, Huntington disease, and type 1 neurofibromatosis |
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Term
Southern blotting
restriction sites (RFLPs) |
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Definition
| Restriction enzymes can cut DNA into fragments, which are sorted according to their length by electrophoresis, transferred to a solid membrane (____), and visualized through the use of labeled probes. This process can detect deletions or duplications of DNA, as well as polymorphisms in ____. |
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Term
| polymerase chain reactions |
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Definition
Is quicker and requires much less DNA for the detection of DNA variation
Heating and cooling cycles are used to denature DNA and then build new copies of a specific primer bound sequence using DNA polymerase. Typically the cycles are repeated 20-30 times producing millions of copies of the original DNA |
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Term
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Definition
| consists of three basic steps: DNA denaturing at high temperature, primer hybridization at a low temperature, and primer extension at an intermediate temperature. The result is a product that consists almost entirely of a specific DNA sequence. |
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Term
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Definition
| allows us to deduce two fundamental concepts of probability, the multiplication rule and the addition rule |
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Term
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Definition
| states that if two trials are independent, then the probability of obtaining a given outcome in both trials is the product of the probabilities of each outcome |
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Term
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Definition
| states that if we want to know the probability of either one outcome or another, we can simply add the respective probabilities together |
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Term
| gene and genotype frequencies |
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Definition
| specify the proportions of each allele and each genotype, respectively, in a population. Under simple conditions these frequencies can be estimated by direct counting |
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Term
| the Hardy-Weinberg principle |
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Definition
| specifies the relationship between gene frequencies and genotype frequencies. It is useful in estimating gene frequencies from disease prevalence data and in estimating the incidence of heterozygous carriers of recessive disease genes. |
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Term
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Definition
| the evolutionary process in which alleles that confer survival or reproductive advantages in a specific environment are selected positively to increase in frequency, and alleles that confer lower survival or reproductive disadvantages are selected negatively so that they decrease in frequency. |
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Term
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Definition
| a random evolutionary process that produces larger changes in gene frequencies in smaller populations |
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Term
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Definition
| small founder populations can experience large changes in gene frequency because of their small size, is a special case of genetic drift |
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Term
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Definition
| The proportion of individuals in a population that carry a specific genotype. (A genotype is an individual’s allelic constitution at a locus.) |
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Term
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Definition
| In a population, the proportion of chromosomes that contain a specific allele. |
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Term
| Hardy-Weinberg Equilibrium |
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Definition
-gene frequencies remain constant from one generation to the next.
-Happens when mating is random and the population is large, with no migration, genetic drift, mutation, or natural selection. |
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Term
| autosomal dominant inheritance |
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Definition
| Only one copy of a mutant allele is necessary for expression of the trait |
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Term
| autosomal dominant pedigree |
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Definition
-Transmission is vertical (from generation to generation)
-Number of affected males and females is equal
-Male-to-male transmission is observed
-Unaffected individuals have unaffected children (exception is decreased penetrance).
-Disorder may arise as a new mutation.
-Phenotype can vary from affected person to affected person in same family |
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Term
| autosomal dominant pedigree |
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Definition
| characterized by vertical transmission of the disease phenotype, a lack of skipped generations, and roughly equal numbers of affected males and females. Father-to-son transmission may be observed |
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Term
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Definition
| The probability that an individual offspring will be affected by the disease in question is termed the ___ |
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Term
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Definition
| The recurrence risk for an autosomal dominant disorder is ___. Because of independence, this risk remains constant no matter how many affected or unaffected children are born |
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Term
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Definition
-The disorder is rarely present in the parents, collateral relatives or ancestors, but may appear in siblings.
-Number of affected males and females is equal.
-Consanguinity is more likely to be present |
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Term
| autosomal recessive pedigree |
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Definition
-Cluster in ethnic groups with relative geographic or religious isolation and increased consanguinity.
-Penetrance is usually complete and there is little phenotypic variability.
-Most of these disorders are enzyme abnormalities. |
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Term
| Quasidominant inheritance |
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Definition
| The recurrence risk for autosomal recessive diseases is usually 25%. ___, with a recurrence risk of 50%, is seen when an affected homozygote mates with a heterozygote. |
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Term
| Quasidominant Inheritance |
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Definition
| Occurs when a carrier of a recessive disease gene mates with an individual who is homozygous for the disease. Roughly half the children will be affected and half will be heterozygous carriers. This pattern mimics that of an autosomal dominant trait. |
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Term
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Definition
| a common cause of the appearance of a genetic disease in a person with no previous family history of the disorder. The recurrence risk for the person's siblings is very low, but the recurrence risk for the person's offspring may be substantially increased |
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Term
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Definition
| Occasionally two or more offspring may present with an autosomal dominant or X-linked disease when there is no family history of the disease. The most likely explanation is |
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Term
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Definition
| The probability of expressing a phenotype given that an individual has inherited a predisposing genotype |
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Term
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Definition
| With ___ penetrance, an individual who has the genotype for a disease may not exhibit the disease phenotype at all, even though they can transmit the disease gene to the next generation |
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Term
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Definition
| A delay in the age of onset of a genetic disease is known as age dependent penetrance. One of the best known examples is ____ |
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Term
Penetrance
Variable expression |
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Definition
| ____ is an all-or-none phenomenon: One either has the disease phenotype or does not. ___ refers to the degree of severity of the disease phenotype |
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Term
| environmental effects, modifier loci, or allelic heterogeneity |
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Definition
| Variable expression of a genetic disease may be caused by |
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Term
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Definition
| Quite commonly, a single disease phenotype is caused by mutations at different loci in different families, which is termed ____ |
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Term
| Adult polycystic kidney disease (APKD) |
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Definition
| is an autosomal dominant disorder in which a progressive accumulation of renal cysts is seen. Occurring in about 1 of every 1000 persons of European descent, this disorder is responsible for 8% to 10% of end-stage renal disease in North America. It can be caused by mutations in genes on either chromosome 16 (PKD1) or chromosome 4 (PKD2). |
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Term
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Definition
Describes genes that have multiple phenotypic effects.
Examples are Marfan syndrome and cystic fibrosis |
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Term
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Definition
| increases the chance that a mating couple will both carry the same disease-causing mutation. It is seen more often in pedigrees involving rare recessive diseases than in those involving common recessive diseases |
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Term
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Definition
| proposed that one X chromosome in females is inactivated. This would result in an equal-ization of X-linked gene products in males and females. |
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Term
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Definition
| stated that X inactivation occurs early in female embryonic development and that the X contributed by the father is inactivated in some cells whereas in other cells the X contributed by the mother is inactivated. |
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Term
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Definition
| The inactive X chromosome, visible as a densely staining chromatin mass in the somatic cells of normal females |
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Term
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Definition
| The number of Barr bodies in somatic cells is always ____ number of X chromosomes. |
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Term
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Definition
| located in the X inactivation center and is required for X inactivation. It encodes an RNA product that coats the inactive X chromosome |
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Term
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Definition
| X inactivation is also associated with methy-lation of the ____, a process that may help to ensure the long-term stability of inactivation. |
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Term
| x-linked recessive inheritance |
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Definition
-Hemizygous males are affected
-Heterozygous female carriers are usually unaffected
-Heterozygous females have 50% chance for having heterozygous carrier daughters and 50% chance for having hemizygous affected sons.
-Affected males will have all normal sons and all heterozygote (carrier) daughters. |
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Term
| x-linked recessive inheritance |
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Definition
-Incidence is much higher in males than females.
-No male-to-male transmission.
-Trait is passed from an affected male to all of his daughters and then to ½ of the daughter’s sons.
-Carrier females may show variable expression of the trait.
-Appearance of “skipped” generations |
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Term
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Definition
Carrier female mates with normal male.
-Daughters will be 50% normal and 50% carriers
-Sons will be 50% normal and 50% affected |
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Term
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Definition
Affected father mates with normal mother
-All of the sons must be normal
-All of the daughters will be carriers |
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Term
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Definition
Affected father mates with carrier mother
-Half of the daughters will be heterozygous carriers, while half, on average, will be homo-zygous for the disease gene and thus affected
-Half of the sons will be normal and half will be affected. It may appear that father-son transmission has occurred, but the affected son has actually received the disease allele from his mother. |
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Term
| x-linked dominant diseases |
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Definition
-Fewer in number and prevalence than X-linked recessive diseases.
-They are about twice as common in females as in males, skipped generations are uncommon, and father-son transmission is not seen.
-Hypophosphatemic rickets, incontinentia pigmenti Type 1, and Rett syndrome |
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Term
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Definition
-Affected fathers cannot transmit the disease to their sons. All of their daughters must inherit the disease gene, so all are affected.
-Affected females are usually heterozygotes and thus have a 50% chance of passing the disease allele to their daughters and sons |
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Term
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Definition
| occurs in only one of the sexes due, for instance, to anatomical differences (inherited uterine or testicular defects) |
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Term
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Definition
| An autosomally transmitted trait that is expressed in both sexes, but with widely different frequencies (e.g. male pattern baldness, congenital adrenal hyperplasia). |
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Term
mitochondrial disease
mitochondrial disease |
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Definition
| Organ systems with large ATP require-ments tend to be the one most seriously affected by _____. The CNS consumes about 20% of the body’s ATP production and is therefore often affected by _____. |
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Term
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Definition
| Each cell contains a population of mtDNA molecules. A single cell can harbor some molecules that have a mtDNA mutation and some that do not. This is called ____ and is an important cause of variable expression in mitochondrial dz. |
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Term
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Definition
| the mtDNA is a mixture of normal and mutant forms |
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Term
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Definition
| the mtDNA is all the same type, ie. all normal or all mutant |
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Term
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Definition
| For some human genes, one of the alleles is transcriptionally inactive (no mRNA is produced), depending upon the parent from whom the allele was received. |
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Term
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Definition
| process of gene silencing is known as ___, and the transcriptionally silenced genes are said to be ____ |
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Term
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Definition
| Imprinted alleles tend to be ____ |
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Term
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Definition
| refers to progressively earlier or more severe expression of a disease in more recent generations. Expansion of DNA repeats has been shown to cause this in some genetic diseases. These diseases can be divided into three major categories, depending on the size of the expansion, the location of the repeat, the phenotypic consequences of the expansion, the effect of the mutation, and the parent in whom large expansions typically occur |
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Term
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Definition
The single most common inherited cause of mental retardation.
Name derived from the fact that the X chromosomes of affected individuals, when cultured in folic acid deficient media, sometimes exhibit breaks and gaps near the tip of the long arm. |
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Term
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Definition
It is the single most common cause of inherited mental retardation
It is characterized by large ears and a long face
It is characterized by macro-orchidism
The degree of mental retardation tends to be milder in females |
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Term
| Chromosomal abnormalities |
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Definition
-Occur in approximately 1 of every 150 live births.
-They are a leading cause of mental retardation and pregnancy loss
-Are seen in 50% of first trimester and 20% of second trimester spontaneous abortions |
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Term
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Definition
| A display of chromosomes, ordered according to length. Depending on the position of the centromere, a chromosome may be acrocentric, submetacentric, or metacentric. |
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Term
| Fluorescence in situ hybridization (FISH) |
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Definition
| A technique in which a labeled probe is hybridized to metaphase, prophase, or interphase chromosomes. It can be used to test for missing or additional chromosomal material as well as chromo-some rearrangements. |
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Term
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Definition
| uses varying combinations of five different fluorescent probes in conjunction with special cameras and image-processing software so that each chromosome is uniquely colored (painted along its entire length with a series of probes) for ready identification. Such images are especially useful for identifying small chromosome rearrangements |
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Term
| Comparative Genomic Hybridization (CGH) |
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Definition
-technique in which differentially labeled DNA from test and control sources is hybridized to normal metaphase chromosomes or probes in microarrays, allows the detection of chromosome duplications and deletions but not balanced rearrangements.
-can detect deletions and duplications shorter than 100 kb and requires only small amounts of DNA. |
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Term
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Definition
-Is seen in only about 1 in 10,000 live births but accounts for 15% of the chromosomal abnormalities occurring at conception
-The most common cause is the fertilization of an egg by two sperm. |
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Term
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Definition
| It has been seen in only a few live births, and those infants survived only for a short period. Can be caused by a mitotic failure in the early embryo in which all of the duplicated chromosomes migrate to one of the two daughter cells. Can also result from the fusion of two diploid zygotes. |
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Term
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Definition
-Karyotype 47, XY, +21 or 47, XX, +21
-Occurs in approx. 1 of every 800 - 1000 live births
-In 1959 the cause was discovered to be the presence of an extra copy of chromosome 21. |
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Term
nondisjuction
sterile
ovulate |
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Definition
-95% of Down syndrome cases are caused by ___, with most of the remaining cases caused by chromosome translocations.
-Males with Down syndrome are almost always ____
-Females can reproduce although 40% fail to ____. |
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Term
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Definition
| The most significant problems include mental retardation, gastrointestinal tract obstruction, congenital heart defects, respiratory tract infections, and leukemia. |
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Term
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Definition
The extra 21st chromosome is contributed by the mother in approx 90% of the cases.
Mosaicism is seen in 2-4% of cases and is often associated with a milder phenotype |
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Term
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Definition
-Known as Edwards syndrome is the second most common autosomal trisomy with a prevalence of about 1 per 6,000 live births.
-It is the most common chromosome abnormality among stillborns with congenital malformations. Fewer than 5% survive to term. |
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Term
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Definition
-Small for gestational age, characteristic facial features, and a distinctive hand abnormality with overlapping fingers, small ears with unraveled helices, short sternum, and short big toes.
-Congenital heart defects, omphalocele, diaphragmatic hernia, and occasionally spina bifida. |
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Term
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Definition
-Patau syndrome is seen in about 1 of every 10,000 lives births.
-Characterized by oral-facial clefts, microphthalmia, and post axial polydactyly
-Malformations of the CNS are frequent as are heart defects and renal abnormalities
-95% die within the first year of life |
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Term
| sex chromosome aneuploidy |
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Definition
| Among live born infants approx 1 in 400 males and 1 in 650 females have some form of _____. |
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Term
| Sex Chromosome Aneuploidy |
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Definition
| Because of X inactivation, the consequences of this class of aneuploidy are less severe than those of autosomal aneuploidy |
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Term
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Definition
-Karyotype 45, X
-Individuals with this syndrome are female and usually have a characteristic phenotype which consists of short stature, sexual infantilism and ovarian dysgenesis, triangular face, webbed neck, broad shield like chest |
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Term
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Definition
-Congenital heart defects are common consisting primarily of coarctation of the aorta and/or bicuspid aortic valve.
-Individuals with this have normal intelligence. |
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Term
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Definition
-Karyotype 47, XXY
-Occurs in approximately 1/500 to 1/1000 live births.
-Common cause of primary hypogonadism in males and most are sterile.
-Tall with disproportionately long arms and legs. |
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Term
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Definition
Reduced IQ although not mentally retarded.
Because of the subtlety of this disorder, many are not diagnosed until after puberty
Maternal age: incidence increases with maternal age |
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Term
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Definition
-47 XXX occurs in approximately 1/1000 females and is benign except for reduced fertility, menstrual irregularities, and mild mental retardation.
-90% of cases are the result of nondisjunction in the mother and the incidence increases with increasing maternal age. |
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Term
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Definition
-Males with this karyotype tend to be taller than average and have a 10-15 point reduction in IQ.
-Higher than average incidence of hyper-activity, ADD, and learning disabilities. |
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Term
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Definition
is the interchange of genetic material between non-homologous chromosomes and are of two types:
-Reciprocal
-Robertsonian |
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Term
| Reciprocal translocations |
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Definition
| Breaks occur in two different chromosomes and the material is mutually exchanged. The resulting chromosomes are called derivative chromosomes. The carrier is usually unaffected but his or her offspring can carry the translocation, or can have duplications or deletions of genetic material. |
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Term
| Robertsonian translocations |
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Definition
| The short arms of two nonhomologous chromosomes are lost and the long arms fuse at the centromere to form a single chromosome. The carriers of this type of translocation are phenotypically normal but have only 45 chromosomes in each cell. They can produce conceptions with monosomy or trisomy. |
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Term
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Definition
| caused by a chromosome break and subsequent loss of genetic material. |
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Term
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Definition
| is an example of a chromosome deletion syndrome and is caused by a deletion of the distal short arm of chromosome 5: 46, XY, del(5p) |
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Term
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Definition
| A subtype of chromosome deletion that can be observed only in balanced chromosomes or, in some cases, using molecular genetics approaches. Syndromes caused by the deletion of a series of adjacent genes are sometimes called contiguous gene syndromes. |
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Term
| Subtelomeric Rearrangements |
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Definition
| Involve deletions or duplications of DNA in the gene-rich regions near telomeres. Rearrangements in this region frequently cause genetic disease. |
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Term
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Definition
A condition in which one parent has contributed two copies of a chromosome and the other parent have contributed none.
This is a cause of Prader-Willi syndrome |
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Term
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Definition
-can arise from unequal crossover, or they can occur among the offspring of reciprocal translocation carriers
-generally produce less serious consequences than deletions do |
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Term
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Definition
| relatively common structural abnormalities and may be either pericentric (including the centro-mere) or paracentric (excluding the centro-mere). |
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Term
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Definition
| formed when a chromosome divides along an axis perpendicular to its usual axis of division. This produces one chromosome with only the short arms and another with only the long arms. |
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Term
| The Philadelphia chromosome |
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Definition
| is associated with chronic myelogenous leukemia. |
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Term
| Chromosome Instability Syndromes |
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Definition
| These syndromes all involve increased frequencies of chromosome breakage and an increased risk of malignancy. All are associated with defects in DNA replication or repair. |
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Term
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Definition
| The incidence of ___ is approx 1/2500 live births, or 10% of all monogenic conditions in children. |
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Term
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Definition
| Most ____ are inherited in an autosomal recessive pattern. The carrier state usually is not associated with morbidity. Carrier and diagnostic testing are becoming widely available for many disorders. |
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Term
glucose and galactose
fructose and glucose. |
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Definition
-Lactose is disaccharide composed of ____
-Sucrose is composed of _____ |
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Term
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Definition
| The most common of the inherited disorders of carbohydrate metabolism. Newborn screening is widespread. Treatment consists of eliminating dietary galactose. If left untreated, children develop liver disease, poor growth, and mental retardation. Mutations in GAL-1-P-uridyl transferase are the most common cause |
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Term
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Definition
| a serious disease with early onset of symptoms; the incidence is 1 in 60,000. The newborn infant normally receives up to 20% of caloric intake as lactose, which consists of glucose and galactose. Without the transferase the infant is unable to metabolize galactose 1-phosphate, the accumulation of which results in injury to parenchymal cells of the kidney, liver, and brain. |
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Term
| cysteine, taurine, tyrosine, histidine and arginine |
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Definition
| are semiessential amino acids in children, because the metabolic pathways that synthesize these amino acids are not fully developed. |
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Term
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Definition
| Defects in the metabolism of phenylalanine (an essential amino acid) cause some of the most widely studied of all metabolic defects |
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Term
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Definition
| Elevated levels of plasma phenylalanine disrupt essential cellular processes in the brain such as myelination and protein synthesis, eventually causing mental retardation. |
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Term
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Definition
| Errors in the ____ result in the accumulation of metabolites that would otherwise have been recycled or eliminated. |
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Term
| Lysosomal Storage Diseases |
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Definition
| These are the prototypical inborn errors of metabolism: disease results from the accumulation of substrate. Accumulation of undegraded molecules results in cell, tissue, and organ dysfunction. |
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Term
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Definition
| a group of diseases caused by a reduced ability to degrade one of more glycosaminoglycans. Glycosaminoglycans are degradation products of proteoglycans found in the extracelluar matrix. |
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Term
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Definition
-Except for X-linked Hunter syndrome , all of these disorders are inherited in an autosomal recessive fashion.
-All are characterized by chronic and progressive multisystem deterioration.
-Hurler, severe Hunter, and Sanfilippo syndromes are characterized by mental retardation. |
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Term
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Definition
| consists of five major biochemical reactions that convert nitrogenous waste products to urea, which is then excreted by the kidney. Defects in this pathway lead to the accumulation of urea precursors, progressive neurologic impairment, and death. The most common defect is X-linked ornithine trans-carbamylase (OTC) deficiency. |
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Term
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Definition
-Results from an excess of copper caused by defective excretion of copper into the biliary tract. This causes progressive liver and neurological abnormalities
-Autosomal recessive
-Decreased serum ceruloplasmin
-Kayser-Fleischer rings |
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Term
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Definition
| the study of the genetic basis for variation in drug response. |
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Term
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Definition
| employs tools for surveying the entire genome to assess multigenic determinants of drug response |
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