population genetics Flashcards
What is species?
a discrete, reproductively defined system of populations with a common evolution
what is a population?
A group of animals of one species which interbreed
what is a gene pool
set of genes and or alleles in the netire population
what is a breed?
a population distinguishable from another of the same species by frequencies of genes, chromosomal variation, or hereditary phenotypic characteristic
what is population genetics
allele frequencies of a population of aniamals
in many species genes are fixed meaning all animals are homozygous for the same allele (all angus are polled)
A dominant and a recessive
Hardy-Weinberg equilibrium?
p2+ 2pq + q2 = 1
gene frequencies
autosomal recessive - q2
frequency of recessive allele the square root of q2
frequency of an allele that is X linked recessive
= frequency in males - XY
or sqrt frequency in females XX
gene frequencies remain stable if?
mating is random
no selection
no mutation
no migration
large population
what happens in domestic animal breeding?
- humasn select which animals to breed
- in wild animals they choose their own mates
- hardy weinburg equilibrium - works for wild but has to be motified for domestic animals
we have to calculate frequencies, if phenotypic selection is used
what is snyders ratio?
based on phenotype - rarely know genome
used to determine proportion of recessive or dominant offspring per parental mating type
What is genetic drift
small subpopulations become increasingly different over generations
Ex. rabbits change frequency changes in each generation
population size influences the allele frequency changes or drift
what is the founder effect
founding a small population (herd)
gene frequency changes are due to chance
what happens in breed introduction?
relatively small number of animals found thhe population
new population could be very differnt from parent population in terms of gene frequency
what is a population bottleneck
severely reduced in numbers for 1 or more generations
What is gene flow
exchange of new alleles between subpopulations
Panmictic populations : random mating in breeding population, exchange of breeding animals
genetic isolates: subpopulation breeds only within itself (closed herd)
what is cline?
phenotypic gradients across a geographical region
gene flow is greatest between adjacent populations
what is migration?
- migration of wild animals could be from their own movement
- in domestic animals, migration can include; putchase, trucking to a new barn or ranch - by owners
- migration of animals in the wild is typically some males and some females
migration in domestication is buying males
what effect of migration or gene flow depends on:
rate of immigration
difference in gene frequencies between the populations
what are import-export regulations
can halt migration
australia demands karyotype on charolais
canada demands no foot and mouth
what does migration do?
- assures a constant source of genetic variation
- retards random drift
- allows spread of a new negative or positive mutation
what is the argument over genetic change
- domestic animal breeders want genetic change
preservationists want no change
what is artificial selection
choice of certain animals as breeding stock, based on certain traits
occasionally this operates counter to natural selection
large domestic turkeys that cant copulate
