Module 13 - Genetics: Genotypes, Gene Action and Gene Interaction

genotype

the genetic make-up of an individual

homozygous

having the same alleles at a particular locus on homologous chromosomes

heterozygous

having different alleles at a particular locus on homologous chromosomes

progeny

descendants or offspring of a given animal or animals

phenotype

an observed characteristic of an animal that is the result of the animal's genes interacting with the environment

phenotypic selection

selection of breeding stock based on observed phenotypes

normal curve OR bell curve

a common continuous statistical distribution that describes the range of phenotypes that are possible for a given trait within a population; the size and shape of the distribution are determined by the population mean and standard deviation

phenotypic mean

statistical average of all phenotypes within the population

phenotypic standard deviation

a statistical measure that indicates the amount of phenotypic variance within a population; describes the width of the normal distribution

dominant allele

an allele that has a stronger influence on a phenotype than its recessive counterpart such that it can partially or fully mask the effect of the recessive allele

recessive allele

an allele that has a weaker influence on a phenotype than its dominant counterpart such that it can be partially or fully masked by the effects of the dominant allele

gene action

describes the ways in which alleles at a given locus interact with each other

complete dominance

a type of gene action in which one allele (the dominant allele) completely masks the effects of the other allele (the recessive allele); the phenotype of the heterozygote will be identical to that of the dominant homozygote

partial dominance

a type of gene action in which the dominant allele does not completely mask the effect of the recessive allele; the phenotype of the heterozygote will more closely resemble that of the dominant homozygote

over-dominance

a type of gene action in which the heterozygote performs outside of the range of the two homozygotes; the phenotype of the heterozygote will more closely resemble that of the dominant homozygote

co-dominance

a type of gene action in which no dominant allele exists; the phenotype of the heterozygote will be exactly intermediate to the two homozygotes

additive gene action

a type of gene action in which no dominant allele exists; the phenotype of the heterozygote will be exactly intermediate to the two homozygotes

epistasis

a phenomenon in which alleles from different loci interact