Mating Systems Flashcards
list and describe the 2 types of mating systems?
- random: Hardy-Weinberg, genotypic frequencies dependent upon allelic frequencies
- non-random: strategic for genetic change
what are the 2 types of strategies for genetic change?
selection and mating systems
describe selection
deciding which individuals to retain as parents who will contribute to subsequent generation
what are the 2 goals of selection?
- increase frequencies of alleles with desirable effects
2. decrease frequency of alleles with undesirable effects
describe mating systems
which males mated to which females
what does the application of mating systems lead to?
further changes in allelic frequency beyond those accomplished by selection
what do mating systems do to genotypic frequencies?
alters them, changes the proportion of homozygous to heterozygous individuals in offspring generation
what are the 2 kinds of mating systems?
random and nonrandom
describe random mating systems
Hardy Weinberg, any male can mate with any female, and there is no attempt by a breeder to pair specific mates
describe what happens in nonrandom mating systems
the expected proportion of homozygous and heterozygous individuals deviate from HW expectations
what two ways is assignment of mates in nonrandom mating systems based on?
- genetic relationship
2. phenotypic similarity
what are the 2 ways of assigning mates based on genetic relationship in nonrandom mating?
- inbreeding
2. outbreeding
what are the two ways of assigning mates based on pehnotypic similarity in nonrandom mating?
- positive assortative
2. negative assortative/dissasortative
what is inbreeding?
attempt to make individuals more homozygous for superior genes of ancestor, mating between members more related than average of population
what is the inbreeding coefficient?
the probability that 2 alleles at a locus are identical by descent (IBD), a reflection of the increased proportion of homozygous loci in an individual, quantified by Fx
what is outbreeding?
increases heterozygosity, used in commercial meat animal production, mating between individuals less related than average of the population
what is the genetic effect of outbreeding?
hybrid vigor, or heterosis
what is phenotypic similarity based on?
performance
what is positive assortative mating?
mating a male and female because they resemble each other closely (for a trait) than if chosen at random from the population
what is negative assortative/dissassortative mating?
mating a male and female because they resemble each other less closely (for a trait) than if chosen at random from the population
what must be true in order for offspring to be considered inbred?
sire and dam must be genetically related
what does Fx (inbreeding coefficient) measure?
the percent increase in homozygous gene pairs in the individual relative to the average of the breed
what will the Fx value of most head of livestock not exceed?
0.5
what does IBS mean?
identical by state, or by chance, no common ancestor
what is the genetic result of inbreeding?
increase in homozygosity beyond what would be found in a randomly mating population
what is linebreeding?
a less intense form of linebreeding to concentrate the genes of one common ancestor by mating individuals within a particular line, designed to maintain a high degree of relationship to a highly regarded ancestor
where is linebreeding most commonly used?
the horse industry
what are the 6 effects of inbreeding?
- Prepotency
- Expression of deleterious recessive alleles
- Inbreeding depression
- Tends to “fix” characteristics (traits) in a population
- Concentrate genes in a population: can be good or bad
- Increases probability of getting similar genes to offspring from ancestor
describe prepotency
performance of offspring is especially like that of the parent
does inbreeding create deleterious recessive alleles?
no, it just increases their expression
describe inbreeding depression
acts of quantitative traits, is a decrease in the performance of inbreds for trait like fertility and survivability, the result of an unfavorable GCV
what is additive genetic relationship?
the proportion of genes which 2 individuals have in common; describes the added genetic likeness of the 2 individuals in question, a numerical value from 0-1
what does genetic relationship attempt to do?
quantify the proportion of genes within 2 individuals that are identical by descent
what is the variable the represents genetic relationship?
Rxy
