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Exam 1 Genetics

TermDefinition
chromosome means colored body; nuclear DNA passed on through gametes by males and females
karyotype an arrayed set of banded chromosomes
diploid 2 copies of each type of chromosome; produced by the fusion of 2 gametes, one from the female and one from the male
homologous chromosome members of a chromosome pair
nonhomologous chromosome chromosomes from different pairs
metacentric chromosome the arms are about equal in length
submetatacentric one arm is shorter that another
acrocentric one arm is extremely short
telocentric centromere is at the end of a single arm
G1 the cell prepares for DNA and chromosome replication
G2 the cell prepares for cell division
S DNA replication
Interphase individual chromosomes are elongated; centrioles are replicated
meiosis process of two successive divisions of a diploid nucleus with one DNA replication cycle resulting in the formation of haploid gametes
Prophase 1 chromosomes become shorter and thicker, crossing over occurs, spindle apparatus forms, nuclear membrane and nucleolus disappear
leptonema early prophase, chromosomes visible, sister chromatids present, cell committed to meiosis
zygonema homologous chromosomes begin to pair and twist around another
pachynema "thick strand", chromosomes very condensed and synapsed, crossing over takes place
diplonema chromosomes begin to move apart
diakineses chiasmata often terminalize; easiest time to count chromosomes
Metaphase 1 nuclear membrane has broken down, spindle apparatus is formed, tetrads align on equatorial plate
Anaphase 1 chromosomes in each tetrad seperate
Telophase 1 tetrads complete their migration to opposite poles
Prophase 2 chromosome contraction
Metaphase 2 centromeres divide and sister chromatids become seperate chromosomes lined up on the equatorial plate
Anaphase 2 centromeres and chromosomes are pulled to opposite spindles
Telophase 2 nuclear membrane forms around the chromosomes and cytokinesis takes place
gene the basic unit of inheritance
allele an alternative form of a gene or region of DNA
locus the location or position on a chromosome of a particular gene
Dominance where the phenotype of the heterozygote is the same as the dominant homozygote
Recessive for the phenotype to be expressed, both alleles must be homozygous
Law of Independent Assortment genes assort independently during meiosis
Complete Dominance a form of dominance in which the expression of the heterozygote is identical to the expression of the homozygous dominant genotype
Partial Dominance the expression of the heterozygote is intermediate to the expressions of the homozygous genotype; favors towards the dominant
No dominance/codominance the expression of the heterozygote is exactly halfway between the phenotype of the homozygotes
Overdominance the expression of the heterozygote is outside the range definded by the phenotype of the homozygous dominant genotypes
Epistasis occurs when the phenotypic expression of a gene at one locus is affected by the alleles of a gene at another locus
Sex-linked inheritance when the gene responsible for the phenotype is located on a sex chromosome
sex-limited trait phenotypic expression is limited to one sex
sex-influenced inheritance phenotypic expression is influenced by the gender of the animal
breeding value the collective genetic merit of an animal when all of its genes are considered
heritability measures the strength of the relationship between the trait and the breeding value
performance testing systematic measurement of performance in a population
Accuracy measure of the strength of the relationship between the true value and the prediction
simply-inherited traits that are affected by only a few genes
polygenic traits controlled by many genes
mating the process that determines which males will be bred to which female(s)
complementarity an improvement in the overall performance in the offspring resulting from mating individuals with different but complimentary breeding values
crossbreeding mating of sires of one breed to dams of another breed
allele frequency the relative abundance or rarity of an allele in a population
random mating a system in which each individual has an equal opportunity to mate with any individual of the opposite sex
migration movement of breeding animals from one population into another pop where the allele frequencies differ
genetic drift changes is gene frequency caused by CHANCE segregation of an allele into the gametes
quantitative traits traits that are measured with numbers on a continuous scale
threshold traits traits where the underlying genetic level has to reach a certain point before phenotypic expression changes
fitness the ability to survive and reproduce
Phenotypic value measure of performance for a trait in an individual
Genotypic value Effect of an individual's genes on its performance for a trait
Environmental effect effect that external (nongenetic) factors have on animal performance
Population mean average phenotypic value of all individuals in a population
Independent/additive gene effects effect of an allele is independent of the effect of the other allele at the same locus and the effects of epistatsis
gene combination value the part of an individual's genotypic value that is due to the effects of combination of genes
temporary environmental effect environmental effect that influences a single performance record of an individual, but does not permanently affect the individual's performance for a repeated trait
paramters summary numbers that describe the whole population; constant; generally unknown
statistics summary numbers calculated from samples and are estimates of parameters
variance a measure of dispersion or differences
standard deviation the square root of the variance; average deviation from the mean
covariance population measure that measures the deviations from the means of two variables
correlation a standardized measure of the the degree of the relationship between 2 traits
phenotypic correlation relationship between the performance in one trait and the performance of another
genetic correlation strength of the relationship between the BV fro one trait and the BV for another
regression coefficient the units of change in Y per unit of change in X
Created by: aly486