Population Drift Impact Analysis
Genetic drift is a mechanism of evolution characterized by random fluctuations in allele frequencies from one generation to the next. The magnitude of this random drift is inversely proportional to population size; it is stronger in smaller populations.
In this scenario:
- Population M has a size of NM = 100 individuals.
- Population N has a size of NN = 1000 individuals.
- Starting allele frequencies are $p = 0.5$ and $q = 0.5$ in both populations.
- The time frame is 100 generations, with no selection acting on the populations.
Due to its smaller size, population M will experience stronger genetic drift than population N. Stronger drift causes allele frequencies ($p$ and $q$) to deviate more significantly and randomly from their initial values over time.
Heterozygosity is quantified as $2pq$. This value is maximized when $p = q = 0.5$ (yielding $2 \times 0.5 \times 0.5 = 0.5$) and decreases as allele frequencies become unequal (i.e., move away from 0.5 towards 0 or 1).
Since genetic drift is stronger in population M, its allele frequencies ($p$ and $q$) are expected to diverge more from 0.5 compared to population N after 100 generations. Consequently, the heterozygosity ($2pq$) in population M is expected to decrease more substantially than in population N.
Therefore, $2pq$ in population M is expected to be lower than $2pq$ in population N.
Important Questions from Genetic drift
- In a diploid population of N individuals, the probability of fixation of a new neutral mutation (assuming no other mutation occurs) is _________.
- A few years ago, a very small population of zebrafish became isolated by a newly built dam. As a result, which statement is most likely to be true about this population of zebrafish now?
- Which two of the following processes can result in a decline in heterozygosity in populations?
I) inbreeding; II) genetic drift; III) mutation; IV) random mating - Which of the following processes typically does NOT contribute to increase in genetic variation?
All else being equal, among isolated populations comprising of 10, 100, 500 and 1000 individuals, the impact of random genetic drift is LOWEST in the population with _____________ individuals.
