Module 5--Population Genetics & Genomics Flashcards
What causes temporal changes in the genetic makeup of a population?
Systematic and random evolutionary forces
What is the Theory of Allele Frequencies?
When the members of a population mate randomly, it is easy to predict the frequencies of the genotypes from the frequencies of their constituent alleles
How to calculate allele frequencies?

Frequency of an allele = number of the allele / total number of alleles
In the example, frequency of LM = (1787 x 2 + 3039) / (1787 + 3039 + 1303) x 2 = 0.53
frequency of LN = (1303 x 2 + 3039) / (1787 + 3039 + 1303) x 2 = 0.47
What is the probability that a homozygous dominant individual will be born?
p x p = p2

What is the probability that a carrier individual will be born?
p x q x 2 = 2pq

What is the probability that a homozygous recessive individual will be born?
q x q = q2

What assumption is made in the Hardy-Weinberg Principle (this table)?

Random mating between individuals in the population
What equation defines the frequency of the three genotypes, under random mating?
p2 + 2pq + q2 = 1
What is the Hardy-Weinberg Principle?
-Describes mathematical relationships between allele frequencies and genotype frequencies
p2 + 2pq + q2 = 1
-Allows the prediction of a population’s genotype frequencies form its allele frequencies
What is the Hardy-Weinberg equilibrium?
The Hardy-Weinberg genotype frequencies persist generation after generation, if mating is random and no differential survival or reproduction exists
How to check for agreement between observed data and predicted numbers?
By calculating chi-square statistic
X2 = Sum [(observed of one genotype-expected of one genotype)2/expected of one genotype]
-If X2 <0.001, population is in HW equilibrium
What effect does mutation have on Hardy-Weinberg equilibrium?
If the rate of mutation from A to a or from a to A changes, then the frequencies of A and a will change in Hardy-Weinberg equilibrium
(So HW equilibrium assumes that there is no mutation in population)
What are the results of non-random mating?
Non-random mating may lead to an excess of homozygous individuals
What is the result of inbreeding/consanguineous mating?
Homozygosity across the whole genome
What is the result of assortative mating/mating between alike individuals?
Homozygosity only in the genes associated with assortative mating, which increases linkage disequilibrium around
What effect does natural selection have on Hardy-Weinberg equilibrium?
Elimination of individuals carrying a deleterious phenotype will drive genotypic and allele frequencies away from H-W equilibrium
What is population subdivision?
When populations separate from one another, they become different
What effect does population subdivision have on Hardy-Weinberg principle?
Differences accumulated between populations violate the Hardy-Weinberg principle of uniform allele frequencies throughout the population
What processes play a major role in genetic differentiation?
- Genetic drift
- Migration
- Natural selection
What is migration?
Introduction of genotypes via migration can alter allele and genotypic frequencies
What is the effect of population merging?
Reduces heterozygosity (Wahlund effect)
What happens if populations remain in Hardy-Weinberg equilibrium?
Population are not evolving
How natural selection changes allele frequencies?
Allele frequencies change systematically in populations because of differential survival and reproduction among genotypes
What is fitness, w?
Ability to survive and reproduce






























