Evolution Set-3

Q1. (In a large randomly mating population the frequency of a recessive phenotype is $9\%$ (i.e. $q^2=0.09$). Under Hardy–Weinberg equilibrium, what is the expected frequency of heterozygotes $2pq$?)

Q2. (A diploid population has effective population size $N_e=25$ and initial heterozygosity $H_0=0.60$ at a neutral locus. Using $H_t = H_0\left(1 - \frac{1}{2N_e}\right)^t$, what is the closest value of heterozygosity after $t=5$ generations under pure genetic drift?)

Q3. (Two populations have different effective sizes ($N_{e1}=100$, $N_{e2}=10{,}000$) but the same neutral mutation rate per gamete $\mu$. Which statement best explains why the long-term substitution rate for neutral mutations is expected to be approximately the same in both?)

Q4. (Assertion (A): Autopolyploid individuals formed by chromosome doubling within a diploid plant population ($2n\rightarrow4n$) can become reproductively isolated from the parental diploids in a single generation.
Reason (R): Crosses between newly formed $4n$ autopolyploids and the $2n$ progenitors produce $3n$ offspring that experience irregular meiosis with unbalanced gametes and very low fertility, greatly reducing gene flow.)

Q5. (Assertion (A): Sympatric speciation driven by disruptive ecological selection is unlikely to complete unless there is strong assortative mating or genetic mechanisms that suppress recombination between loci for ecological adaptation and mating preference (e.g., inversions).
Reason (R): Recombination (rate $r$) breaks down linkage disequilibrium between alleles for habitat use and mating preference, preventing the build-up of the genetic associations required for reproductive isolation.)

Q6. In a large randomly mating population the frequency of individuals showing a recessive phenotype is $9\%$. Assuming Hardy–Weinberg equilibrium, what is the expected frequency of heterozygotes in the population?

Q7. A population has allele frequencies $p=0.6$ and $q=0.4$ and is initially in Hardy–Weinberg proportions. Fitnesses are $w_{AA}=1.0,\; w_{Aa}=0.9,\; w_{aa}=0.7$. After one generation of selection, what is the new frequency of allele $A$? (Round to two decimal places.)

Q8. Two species show $12\%$ sequence divergence in a protein. If the substitution rate per lineage is $0.6\%$ per million years and pairwise divergence is given by $d=2rt$, estimate the time since their common ancestor (in million years).

Q9. Assertion (A): A severe population bottleneck reduces genetic variability (heterozygosity) and increases the relative importance of genetic drift.
Reason (R): A bottleneck raises the effective population size $N_e$, so selection becomes more efficient compared to drift.

Q10. An island population initially fixed for allele $a$ receives migrants from a mainland fixed for allele $A$ at rate $m=0.01$ per generation. On the island allele $A$ is deleterious with selection coefficient $s=0.05$ against it. Under migration–selection balance the equilibrium frequency of $A$ is approximately $q^*\approx \dfrac{m}{s}$. What is the expected equilibrium frequency of $A$ on the island?