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Genetics Ch. 1-4
Genetics Essentials
138
Biology
Undergraduate 2
01/28/2010

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Term
What are the three divisions of Genetics?
Definition
Transmission Genetics, Molecular Genetics, Population Genetics
Term
Genome
Definition
A complete set of genetic instructions for any organism - all are encoded in nucleic acids (either DNA or RNA)
Term
Transmission Genetics
Definition
also known as 'Classical Genetics' - it encompasses the basic principles of heredity and how traits are passed from one generation to the next
Term
Molecular Gnetics
Definition
concerns the chemical nature of the gene itself: how genetic information is encoded, replicated, and expressed.
Term
Population Genetics
Definition
explores the genetic composition of groups of individual members of the same species (populations) and how that composition changes over time and geographic space.
Term
Model Genetic Organism
Definition
organisms having characteristics that make them particularly useful for genetic analysis and about which a tremendous amount of genetic information has accumulated.
Term
pangenesis
Definition
suggests that specific pieces of information travel from various parts of the body to the reproductive organs, from which they are passed to the embryo
Term
Inheritance of acquired characteristics
Definition
traits acquired in one's lifetime become incorporated into one's hereditary information and are passed on to offspring; example - musical parent = musical kid
Term
Preformationism
Definition
all traits would be inherited from only one parent - from the father if the homunculus was in the sperm or from the mother if it was in the egg.

Homunculus = tiny adult..
Term
Blending Inheritance
Definition
offspring are a blend, or mixture, of parental traits - suggests that genetic material itself blends (like blue + yellow = green)
Term
Cell Theory
Definition
all life is composed of cells, cells arise only from preexisting cells and the cell is the fundamental unit of structure and function in living organisms
Term
Germ-Plasm Theory
Definition
the cells in the reproductive organs carry a complete set of genetic information that is passed to the egg and sperm
Term
Eukaryotic Cell
Definition
have a nucleus, containing DNA
Term
Prokaryotic Cell
Definition
has DNA, no nucleus though
Term
Gene
Definition
a basic unit of hereditary information -an inherited factor that determines a characteristic
Term
Allele
Definition
varient forms of a gene, arising through mutation- one or two or more alternate forms of a gene
Term
Genotype
Definition
the set of genes or alleles inherited by an organism from its parent(s)
Term
Phenotype
Definition
the expression of the genes of a particular genotype
Term
Chromosome
Definition
structures consisting of DNA and associated with proteins
Term
DNA
Definition
contains genetic information
Term
Homologous pair (chromosomes)
Definition
usually alike in structure and size, each carries genetic information for the same set of hereditary characteristics
Term
diploid
Definition
cells that have 2 sets of genetic information
Term
haploid
Definition
cells with a single set of chromosomes (only one copy of each gene)
Term
Telomere
Definition
the natural ends (tips) of a linear chromosome, serve to stabilize the chromosome ends.
Term
Centromere
Definition
the attachment point for spindle microtubules - appears as as a constricted region on the sister chromatids
Term
Metacentric
Definition
found in the center
Term
Submetacentric
Definition
found above/below the middle
Term
Acrocentric
Definition
towards the end (tips)
Term
Telocentric
Definition
At the ends (tips)
Term
Interphase
Definition
the period between cell divisions, in which the cell grows, develops, and prepares for cell division
Term
M phase
Definition
the period of active cell division, includes Mitosis - the process of nuclear division, and cytokinesis - cytoplasmic division
Term
Prophase
Definition
chromosomes condense and mitotic spindle forms
Term
Prometaphase
Definition
Nuclear envelope disintegrates, and spindle microtubules anchor to kinetochores
Term
Metaphase
Definition
Chromosomes align on the spindle-assembly checkpoint
Term
Anaphase
Definition
sister chromatids separate, becoming individual chromosomes that migrate toward spindle poles.
Term
Telophase
Definition
chromosomes arrive at spindle poles, the nuclear envelope re-forms, and the condensed chromosomes relax
Term
Cytokinesis
Definition
Cytoplasm divides; cell wall forms in plant cells
Term
Meiosis
Definition
consists of a single nuclear division and is usually accompanied by a single cell division (consists of two divisions)
Term
Fertilization
Definition
two haploid gametes fuse and restore chromosome number to its original diploid value
Term
Prophase 1
Definition
a lengthy stage in which the chromosomes form homologous pairs and crossing over takes place
Term
Synapsis
Definition
the fusion of chromosome pairs at the start of meiosis
Term
Bivalent
Definition
a pair of homologous chromosomes
Term
Tetrad
Definition
a group or set of four
Term
Metaphase 1
Definition
Homologous pairs of chromosomes line up along the metaphase plate
Term
Anaphase 1
Definition
Homologous chromosomes separate and move toward opposite poles
Term
Telophase 1
Definition
Chromosomes arrive at the spindle poles and the cytoplasm divides
Term
Interkinesis
Definition
the nuclear membrane re-forms around the chromosomes clustered at each pole, the spindle breaks down, and the chromosomes relax
Term
Prophase 2
Definition
The chromosomes recondense
Term
Metaphase 2
Definition
individual chromosomes line up on the equatorial plate
Term
Anaphase 2
Definition
sister chromatids separate and move toward opposite poles
Term
Telophase 2
Definition
Chromosomes arrive at the spindle poles and the cytoplasm divides
Term
Recombination
Definition
creating new combinations of alleles on a chromatid
Term
Spermatogenesis
Definition
production of gametes in a male animal
Term
Spermatogonia
Definition
a cell produced at an early stage in the formation of spermatozoa, formed in the wall of a seminiferous tubule and and giving rise by mitosis to spermatocytes
Term
Primary Spermatocyte
Definition
Spermatogonium that has entered prophase 1
Term
Spermatids
Definition
an immature male sex cell formed from a spermatocyte that can develop into a spermatozoon without further division
Term
Oogenesis
Definition
production of gametes in a female animal
Term
Oogonia
Definition
an immature female reproductive cell that gives rise to primary oocytes by mitosis
Term
Primary Oocyte
Definition
oogonium that has entered prophase 1
Term
First Polar Body
Definition
One of the products of meiosis 1 in oogenesis; contains half the chromosomes but little of the cytoplasm
Term
Ovum
Definition
a mature female reproductive cell
Term
Microsporocytes
Definition
diploid reproductive cells found in the male part of the flower (stamen)
Term
microspores
Definition
the smaller of the two kinds of spore produced by some ferns
Term
megasporocytes
Definition
diploid reproductive cells found in the female part of the flower (the ovary)
Term
megaspores
Definition
the larger of the two kinds of spores produced by some ferns
Term
Second Polar Body
Definition
one of the products of meiosis 2 in oogenesis; contains a set of chromosomes but little of the cytoplasm
Term
Secondary Spermatocyte
Definition
product of meiosis 1 in male animals
Term
Secondary Oocyte
Definition
one of the products of meiosis 1 in female animal; receives most of the cytoplasm
Term
character/characteristic
Definition
an attribute of feature
Term
Heterozygote
Definition
an individual organism possessing two different alleles at a locus
Term
Homozygote
Definition
an individual organism possessing two of the same alleles at a locus
Term
Monohybrid Cross
Definition
a cross between parents that differed in a single characteristic
Term
P Generation
Definition
the first generation of a cross (parents)
Term
F1 Generation
Definition
the offspring from the parents in the P gerneration
Term
Reciprocal Cross
Definition
crosses in which the phenotypes of the male and female parents are reversed. For example, in one cross, a short male is crossed with a tall female.
Term
F2 Generation
Definition
Offspring of the F1 generation in a genetic cross; the third generation of a genetic cross.
Term
Principle of Segregation
Definition
each individual diploid organism possesses two alleles for any particular characteristic
Term
The Concept of Dominance
Definition
when two different alleles are present in a genotype, only the trait encoded by one of them - the dominant allele - is observed in the phenotype
Term
Probability
Definition
the likelihood of the occurrence of a particular event
Term
Multiplication rule
Definition
the probability of two or more independent events occurring together is calculated by multiplying their independent probabilities
Term
Addition Rule
Definition
the probability of any one of two or more mutually exclusive events is calculated by adding the probabilities of these events
Term
Testcross
Definition
which one individual of unknown genotype is crossed with another individual with a homozygous recessive genotype for the trait in question.
Term
Incomplete Dominance
Definition
the trait shown when the heterozygote has a phenotype intermediate between the phenotypes of the homologous
Term
Wild Type
Definition
the trait or allele that is most commonly found in natural (wild) populations
Term
Dihybrid Cross
Definition
a cross between two individuals that differ in two characteristics - more specifically a cross between individuals that are homozygous for different alleles at the two loci (AA BB x aa bb); also refers to a cross between two individuals that are both heterozygous at two loci (AaBb x Aa Bb).
Term
Principle of Independent assortment
Definition
Important principle of heredity discovered by Mendel that states that genes encoding different characteristics (genes at different Loci) separate independently; applies only to genes located on different chromosomes or to genes far apart on the same chromosome
Term
Chi Squared Test
Definition
statistical test used to evaluate how well a set of observed values fit the expected values. The probability associated with a calculated chi-squared value is the probability that the differences between the observed and the expected values may be due to chance.
Term
Pedigree
Definition
a pictorial representation of a family history, essentially a family tree that outlines the inheritance of one or more characteristics
Term
proband
Definition
the person from whom the pedigree is initiated - usually designated by an arrow
Term
consanguinity
Definition
mating between closely related people
Term
Sex
Definition
male or female
Term
Sex Determination
Definition
Specifications of sex (male or female). Sex determining mechanisms include chromosomal, genic, and environmental sex-determing systems.
Term
Sex Chromosome
Definition
Chromosomes that differ morphologically or in number in males and females
Term
Autosome
Definition
chromosome that is the same in males and females; nonsex chromosome.
Term
heterogametic sex
Definition
the sex (male or female) that produces two types of gametes with respect to sex chromosomes. For example, in the XX--XY sex determining system, the male produces both x bearing and y bearing gametes
Term
homogametic sex
Definition
the sex (male or female) that produces gametes that are all alike with regard to sex chromosomes. For example, in the XX--XY sex determining system, the female produces only X bearing gametes.
Term
Pseudoautosomoal region
Definition
small region of the X and Y chromosomes that contains homologous gene sequence
Term
Genic sex Determination
Definition
Sex determination in which the sexual phenotype is specified by genes at one or more loci, but there are no obvious differences in the chromosomes of males and females
Term
Genic Balance system
Definition
sex-determining system in which sexual phenotype is controlled by a balance between genes on the X chromosome and genes on the autosomes.
Term
X:A ratio
Definition
ratio of the number of x chromosome to the number of haploid autosomal sets of chromosomes; determines sex in fruit flies.
Term
Turner syndrome
Definition
Human condition in which cells contain a single X chromosome and no Y chromosome (XO). Persons with turner syndrome are female in appearance but do not undergo puberty and have poorly developed female secondary sex characteristics; most are sterile but have normal intelligence.
Term
Klinefelter syndrome
Definition
Human condition in which cells contain one or more y chromosome along with multiple x chromosomes (most commonly XXY but may also be XXXY, XXXXY, or XXYY). - persons are male in appearance butfrequently possess small testes, some prest enlargement, and reduced facial and pubic hair; often taller than normal and sterile, most have normal intelligence.
Term
triplo-x syndrome
Definition
Human condition in which cells contain three x chromosomes. A person with triplo-x syndrome has a female phenotype without distinctive features other than a tendency to be tall and thin; a few such women are sterile, bur many menstruate regularly and are fertile.
Term
Sex-determining region Y (SRY) gene
Definition
On the Y chromosome, a gene that triggers male development; also known as the testis-determining factor (TDF) gene.
Term
sex-linked characteristics
Definition
characteristic determined by a gene or genes on sex chromosomes
Term
x-linked characteristic
Definition
characteristic determined by a gene or genes on the x chromosome
Term
y-linked characteristic
Definition
characteristic determined by a gene or genes on the y chromosome
Term
hemizygosity
Definition
Possession of a single allele at a locs. Males of organisms with XX-XY sex determination are hemizygous for X-linked loci, because their cells prevent damage from such stressing agents.
Term
dosage compensation
Definition
Equalization in males and females of the amount of protein produced by X-linked genes. In placental mammals , dosage compensation is accomplished by the random inactivation of one X chromosome in the cells of females.
Term
barr body
Definition
Condensed, darkly staining structure that is found in most cells of female placental mammals and is an inactivated X chromosome.
Term
lyon hypothesis
Definition
proposes that one x chromosome in each female cell becomes inactivated (a barr body) and suggests that which X becomes inactivated is random and varies from cell to cell
Term
codominance
Definition
Type of allelic interaction in which the heterozygote simultaneously expresses traits of both homozygotes
Term
incomplete penetrance
Definition
refers to a genotype that does not always express the expected phenotype. Some individuals possess the genotype for a trait but do not express the phenotype
Term
penetrance
Definition
percentage of individuals with a particular genotype that express the phenotype expected of the genotype
Term
expressivity
Definition
degree to which a trait is expressed
Term
lethal allele
Definition
causes the death of an individual organism, often early in development, and so the organism does not appear in the progeny of a genetic cross. Recessive lethal alleles kill individual organisms that are homozygous for the allele; dominant lethals kill both heterozygotes and homozygotes
Term
multiple alleles
Definition
presence in a group of individuals of more than two alleles at a locus. Although, for the group, the locus has more than two alleles, each member of the group has only two of the possible alleles.
Term
gene interaction
Definition
interaction between genes at different loci that affect the same characteristic
Term
epistasis
Definition
type of gene interaction in which a gene at one locus masks or suppresses the effects of a gene at a different locus.
Term
epistaitc gene
Definition
masks or suppresses the effect of a gene at a different locus.
Term
hypostatic gene
Definition
gene that is masked or suppressed by the action of a gene at a different locus
Term
complementation test
Definition
test designed to determine whether two different mutations are at the same locus (are allelic) or at difrerent loci (are nonallelic). Two individuals that are homozygous for two independently derived mutations are crossed, producing F1 progeny that are heterozygous for the mutations. If the mutations are at the same locus, the F1 will have a mutation phenotype. If the mutations are at different loci, the F1 ill have a wild-type phenotype.
Term
complementation
Definition
wo different mutations in the heterozygous are exhibited as the wild-type phenotype; indicates that the mutations are at different loci
Term
sex-influenced characteristic
Definition
Encoded by autosomal genes that are more readily expressed in one sex. For example, an autosomal dominant gene may have higher penetrance in males than in females or an autosomal gene may be dominant in males but recessive in females.
Term
sex-limited characteristic
Definition
Encoded by autosomal genes and expressed in only one sex. Both males and females carry genes for sex-limited characteristics, but the characteristics appear only one of the sexes.
Term
cytoplasmic inheritance
Definition
Inheritance of characteristics encoded by genes located in the cytoplasm. Because the cytoplasm is usually contributed entirely only by one parent, most cytoplasmically inherited characteristics are inherited from a single parent.
Term
genetic maternal effect
Definition
Determines the phenotype of an offspring. Offspring inherits genes for the characteristics from both parents, but the offspring's phenotype is determined not by its own genotype but by the nuclear genotype of its mother.
Term
genomic imprinting
Definition
Differential expression of a genet that depends on the sex of the parent that transmitted the gene. If the gene is inherited from the father, its expression is different from that if it is inherited from the mother.
Term
epigenetics
Definition
Phenomena due to alterations to DNA that do not include changes in the base sequence; often affect the way in which the DNA sequences are expressed. Such alterations are often stable and heritable in the sense that they are passed from one cell to another.
Term
norm of reaction
Definition
range of phenotypes produced by a particular genotype in different environmental conditions
Term
temperature-sensitive allele
Definition
expressed only at certain temperatures
Term
phenocopy
Definition
phenotype that is produced by environmental effects and is the same as the phenotype produced by a genotype.
Term
discontinuous chracteristc
Definition
Exhibits only a few, easily distinguished phenotypes. An example is seed shape in which seeds are either round or wrinkled
Term
continuous characteristic
Definition
Displays a large umber of possible phenotypes that are not easily distinguished, such as human height
Term
quantitative chracteristic
Definition
Continuous characteristic; displays a large number of possible phenotypes which must be described by a quantitative measurement.
Term
polygenic characteristic
Definition
encoded by genes at many loci
Term
pleiotropy
Definition
a single genotype influences multiple phenotypes
Term
multifactorial chracteristic
Definition
determined by multiple genes and environmental factors
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