Cycle 6 Flashcards
Families to Populations
Q1: What is an allele frequency?
Q2: How is it calculated?
A1: The proportion of a specific allele (e.g., A1 or A2) in a population’s gene pool.
A2: By dividing the number of copies of the allele by the total number of alleles in the population.
Q: What are the conditions for a population to be in Hardy-Weinberg Equilibrium?
- Large population size (no genetic drift).
- Random mating.
- No mutations.
- No migration (gene flow).
- No natural selection.
Q: What does HWE signify?
A: It signifies that allele frequencies in a population remain constant across generations, meaning no evolution is occurring.
Q: What are the genotype frequency equations in HWE?
f(A1A1) = 𝑝^2
f(A1A2) = 2𝑝𝑞
f(A2A2) = 𝑞^2
Where 𝑝 = frequency of A1, and 𝑞 = frequency of A2.
Q1: What happens during selection against harmful dominant alleles?
Q2: What about harmful recessive alleles?
A1: Selection eliminates all copies of the dominant allele from the population quickly.
A2: They decrease in frequency but are rarely fully eliminated because they can “hide” in heterozygous carriers.
Q1: How does heterozygote advantage affect genetic variation?
Q2: What about heterozygote disadvantage?
A1: Maintains both alleles in the population, increasing long-term genetic variation.
A2: Removes genetic variation by favoring the more common allele and driving the rarer allele to extinction.
Q1: What is genetic drift?
Q2: What are two examples of genetic drift?
A1: Random changes in allele frequencies due to chance, most impactful in small populations.
A2: Bottleneck Effect: A population size drastically reduces (e.g., natural disaster).
Founder Effect: A small group starts a new population with random allele representation.
Q1: What happens with selection against harmful dominant alleles?
Q2: What happens with harmful recessive alleles?
A1: Eliminates all copies quickly since the dominant phenotype is visible.
A2: Decreases slowly and rarely reaches zero because recessive alleles can “hide” in heterozygous individuals.
Q1: What is absolute fitness (W)?
Q: How is relative fitness (w) calculated?
A1: Measurable survival or reproduction success (e.g., lifespan or egg production).
A2: 𝑤 = AbsoluteFitness / BestAbsoluteFitness , ranges from 0 to 1.
Q1: What is assortative mating?
Q2: What is disassortative mating?
A1: Individuals prefer mates with similar phenotypes (e.g., white geese mate with white geese).
A2: Preference for mates with different phenotypes (e.g., blue eyes mate with brown eyes).
Q: How does inbreeding affect a population?
A: Increases homozygosity, raising the chance of expressing harmful recessive alleles, but does not change allele frequencies. Additionally, it makes populations more vulnerable to genetic disorders.
Q: In a population of 100 pigs, 36 are BB, 48 are BR, and 16 are RR. What is the frequency of the R allele?
A: Total alleles = 100 x 2 = 200
R alleles = 16 × 2 + 48 = 80
q = 80 / 200 = 0.4
