Measuring Genetic Diversity in Populations Flashcards
Polymorphism
A genetic locus that has two or more forms or alleles, and the probability of encountering a polymorphic locus among all loci in a population
What is the equation for polymorphism?
P=number of polymorphic loci/total number of loci
What is average heterozygosity?
The proportion of heterozygous individuals in a population measured across several loci
H=£Hi/N
H is average heterozygosity at locus i and N is the total number of loci in the estimate
What is a bottle neck
When a population declines to very few individuals
Inbreeding depression
Reduced reproduction and survival frequently observed in small, inbred populations
What is the basic rule of conservation genetics?
Selection for performance and Fertility can balance inbreeding depression if change in the inbreeding coefficient is no more than 1% per generation. Usually 50 minimum
How long does low genetic variation persist after a bottleneck?
Generations, even after population size recovery
What affects small populations after a prolonged bottleneck?
Genetic drift
What is the formula for the change in frequency of a randomly selected allele in one generation?
Delta q= (q(1-q))/2Ne
Equation for degree of decline in heterozygosity
Ht=H0{1-1(2N)}^t
What is the minimum population size needed to reduce drift?
500
What is the equation for the effect of mutations on genetic variability and heterozygosity
Delta H= -H/(2N)+mH = H(m-1/(2N)) where m=the addition of heterozygosity through mutation
Equilibrium is reached at H=2Nm
What is the effective size of a population effected by?
Variance in progeny numbers, differential sex ratios, fluctuations in total numbers, deviations from random Mating Systems
The effect of the number of progeny on Ne
Ne= (4N)/(2+sigma^2)
Hedgecock effect
When a populations effective size is much smaller than its census size
What is the expected number of alleles remaining after a genetic bottleneck?
m-£(1-Pj)^(2Ne)
Who experienced a more dramatic loss of genetic variation?
The elephant seals had more loss than the Guadalupe fur seals
What is the central dogma of conservation genetics?
Low levels of genetic variation may substantially increase the probability that a species may go extinct
