Fixation Probability in Diploid Population
In population genetics, the probability of a new neutral mutation becoming fixed (i.e., reaching a frequency of 1.0) in a diploid population is a key concept.
Understanding Neutral Mutations
A neutral mutation does not confer any selective advantage or disadvantage. Its fate in the population is primarily determined by random genetic drift.
Fixation Probability Formula
For a diploid population of effective size N, the probability of a new neutral mutation eventually becoming fixed is given by the formula:
$ P_{fix} = \frac{1}{2N} $
This formula assumes that the mutation arises initially in a single copy (heterozygous state) in a diploid organism.
Analyzing Population Size Effect
The formula shows that the probability of fixation is inversely proportional to the population size (N). Larger populations have a lower probability of fixation for a neutral mutation due to the stronger effect of random drift overwhelming the initial introduction.
Options Overview
Let's review the given options:
| Option 1 | 1/N |
| Option 2 | 2/N |
| Option 3 | 1/(2N) |
| Option 4 | 1/(4N) |
Conclusion
Based on the standard formula in population genetics, the probability of fixation for a new neutral mutation in a diploid population of size N is 1/(2N).
Important Questions from Genetic drift
- Which one of the following statements about genetic drift is accurate?
- 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 In a population of birds on an island, the average beak size reduced over one generation. A researcher estimated the association between beak size and relative fitness, shown in the graph. The estimated slope was –0.05 with a 95% confidence interval of -0.15 to 0.09.
Which one of the following evolutionary processes acting on beak size is the most likely reason for the observed reduction in beak size?
- Two isolated populations X and Y have 100 and 10000 individuals, respectively. Both populations have the same starting allele frequencies of p=0.5 and q=0.5. After 1000 generations of genetic drift, which of the following statements is true about the heterozygosity at this locus in these two populations?
