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Biology 1402-Held
Test 2
49
Biology
Undergraduate 1
02/12/2008

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Term
Down Syndrome
Definition
A human genetic disorder resulting from the presence of an extra chromosomes 21; characterized by heart and respiratory defects and varying degrees of mental retardation
Term
Nondisjunction
Definition
An accident of meiosis or mitosis in which a pair of homologous chromosomes or a pair of sister chromatids fail toseparate at anaphase.
Term
Deletion
Definition
The loss of one or more nucleotides from a gene by mutation; the loss of fragment of a chromosome.
Term
Duplication
Definition
Repetition of part of a chromosome resulting from fusion with a fragment from a homologous chromosome; can result from an error in meisosis or from mutagenesis
Term
Inversion
Definition
A change in a chromosome resulting from reattachment of a chromosome fragment to the orginial chromosome, but in a reverse direction. Mutagens and errors during meiosis can cause this
Term
Translocation
Definition
A change in a chromoome resulting from a chromosomal fragment attaching to a nonhomologous chromosome; can occur as a result of an error in meiosis or from mutagenesis
Term
Carrier
Definition
An individual who is heterozygous for a recessively inherited disorder and who therefore does not show symptoms of that disorder
Term
Cystic Fibrosis
Definition
A genetic disease that occurs in people with two copies of a certain recessive allele; characterized by an excessive secretion of mucus and vulnerability to infection; fatal if untreated
Term
Achondroplasia
Definition
A form of human dwarfism caused by a single dominant allele; the homozygous condition is lethal.
Term
Huntington's Disease
Definition
A human genetic disease caused by a dominant allele; charactierzed by uncontrollable body movements and degeneration of the nervous system; usually fatal 10 to 20 years after the onset of symptoms
Term
Alzheimer's Disease
Definition
An age-related dementia (mental deterioration) characterized by confusion, memory loss and other symptoms.
Term
Aminocentesis
Definition
A technique for diagnosing genetic defects while a fetus is in the uterus. A sample of amiotic fluid, obtained via a needle inserted into the amnion, is analyzed for telltale chemicals and defective fetal cells.
Term
Chronic Villi Sampling
Definition
A technique for diagnosing genetic defects while the fetus is in the uterus. A small sample of the fetal portion of the placenta is removed and analyzed
Term
Ultrasound
Definition
A technique for examining a fetus in the uterus. High-frequency sound waves echoing off the fetus are used to produce an image of the fetus
Term
Self-Fertilize
Definition
The fusion of sperm and egg produced by the same individual organism.
Term
Cross-Fertilization
Definition
The fusion of sperm and egg derived from two different individuals.
Term
Pure-Breeding Strain
Definition
Crosses between identical homozygotes
Term
Hybrid
Definition
The offspring of parents of two different species or of two different varieties of one species; the offspring of two parents that differ in one or more inherited traits; an individual that is heterozygous for one or more pairs of genes
Term
Allele
Definition
An alternative form of gene
Term
Gene
Definition
A discrete unit of heredity information consisting of a specific nucleotide sequence in DNA (or RNA, in some viruses). Most of eukaryote's are located in its chromosomal DNA; a few are carried by the DNA of mitochondria and chloroplasts
Term
Locus
Definition
The particular site where a gene is found on a chromosome. Homologous chromosomes have corresponding genes of these
Term
Dominant Allele
Definition
In a heterozygote, the allele that determines the phenotype with respect to a partcular gene.
Term
Recessive Allele
Definition
In a heterozygous individual, the allele that has no noticeable effect on the phenotype.
Term
Homozygous
Definition
Having two identical allelesfor a given gene.
Term
Heterozygous
Definition
Having two different alleles for a given gene.
Term
Punnett Square
Definition
A diagram used in the study of inheritance to show the results of random fertilization
Term
Genotype
Definition
The genetic makeup of an organism.
Term
Phenotype
Definition
The expressed traits of an organism.
Term
Monohybrid Cross
Definition
An experimental mating of individuals differing at one genetic locus.
Term
Dihybrid Cross
Definition
An experimental mating of individuals differing at two genetic loci.
Term
Testcross
Definition
The mating between an individual of unknown genotype for a particular characteristic and an individual that is homozygous recessive for that same characteristic.
Term
Incomplete Dominance
Definition
A type of inheritance in which the phenotype of a heterozygote (Aa) is intermediate between the phenotypes of the two types of homozygoes (AA and aa)
Term
Codominance
Definition
Inheritance pattern in which a heterozygote expresses the distince trait of both alleles
Term
Pleitropy
Definition
The control of more than one phenotypic characteristic by a single gene
Term
Polygenic Trait
Definition
The additive effect of two or more gene loci on a single phenotypic characteristic
Term
Epistasis
Definition
One gene suppresses or "dominates" a different gene rather than an allele
Term
Mosaicism
Definition
A trait of female mammals due to inactivation of one X chromosome in every cell
Term
Dosage Compensation
Definition
A trick for equalizing the "dose" of X genes in XX vs. XY individuals
Term

Genetic Recombination

(Crossing Over)

Definition
The production, by crossing over and/or independent assortment of chromosomes during meiosis, of offspring with allele comvinations different from those in the parents. The term may also be used more specifically to mean the production by crossing over of eukaryotic or prokaryotic chromosomes with gene combinations different from t hose in the original chromosomes.
Term
 "Particulate" Theory
Definition
Traits are inherited like particles = genes
Term
P generation
Definition
The parent individuals from which offspring are derived in studies of inheritance; stands for parental
Term
F1 Generation
Definition
The offspring of two parental individuals; stands for first filial
Term
F2 Generation
Definition
The offspring of the F1 generation; stands for second filial
Term
Sex Chromosome
Definition
A chromosome that determines whether an individual is male or female
Term
Autosomes
Definition
A chromosome not directly involved in determining the sex of an organism; in mammals, any chromosome other than x or y
Term
Criss-Cross Inheritance
Definition
How sex-lined (X-chromosomes) genes are passed from Mom to son
Term
Wild Type Allele
Definition
The phenotype most commonly found in nature
Term
Mutation
Definition
A change in the nucleotidesequence of DNA; the ultimate source of genetic diversity
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