Genes in Populations - week 3 Flashcards
what is the role of the animal breeder
to change populations, not individuals
what is a gene frequency/ allelic frequency
the relative frequency of a particular allele in a population
what is gene frequency/ allelic frequency a measure of
how common a particular allele is in a population
what does the relative frequency range from
0-1
what is the frequency if the allele frequency does not exist in a population
zero 0
what is the frequency if it is the only allele in the population
one 1
what is the frequency if it comprises 47% of the genes at locus in a population
the frequency is 0.47
what does p represent
frequency of the dominant allele
what does q represent
frequency of the recessive allelle
what does p+q always =
1
what is genotypic frequency
is the relative frequency of a one - locus genotype in a population
what does P represent
homozygous dominant genotypic frequency
what does H represent
heterozygous genotypic frequency
what does Q represent
homozygous recessive genotypic frequency
what does P+Q+H=
1
what is selection?
selection determines which animals breed
what is the effect of selection from a population genetic viewpoint
increase the frequency of favourable alleles
what is the result of selection
the next generations should have better breeding values (set of genes)
who invented Hardy weinberg equilibrium 1908
George Hardy - british mathematicain
Wilhelm weinbery - german physician
what does the Hardy-Weinberg Equilibrium allow us to predict
the offspring genotype frequency using the parental genotype frequency
what is the basic law of mendelian genetics
law of segregation
what is the basic law of population genetics
hardy-Weinberg law
(p+q)^2
1^2
p^2 +2pq+q^2=1
ratio: 1:2:1
are domestic population in equilibrium
NO
definition of equilibrium
that frequencies do not change between generations
list 4 ways to change gene frequencies
- random genetic drift
- mutation
- migration
- selection - of most interest to animal breeders
Effect of inbreeding on gene breeding
- increase homozygous dominant and recessive.
- decrease heterozygous genotype
Effect of crossbreeding on gene frequency
increase heterozygote
- decrease homoezygote
increase genetic variation
random genetic drift
- random change due to chance
- H-W assumes large populations
- we with small populations
what reduces risk of random genetic drift
increasing population size
what is effective population (Ne)
effective number of breeding animals
Ne = 2 x number of mating pairs
what is the equation of effective population
Ne=4NmNf / (Nm+Nf)
what is mutation
biochemical change in DNA sequence
u = mutation rate from A(dominant) to a (recessive)
- u=1/25,000
v = mutation rate from a to A
- v = 1/250,00
What is migration
introduction of alleles from outside the population
- Natural migration
- Artificial migration eg crossbreeding
why do animal breeding carry out selection
for economically important traits
- quantitative
- qualitative
what are qualitative traits
controlled by single gene
what are quantitative traits:
controlled by many genes
