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
- Two isolated populations M and N have population sizes of 100 and 1000 individuals, respectively. The starting allele frequencies p and q are 0.5 in both populations. Assuming no selection, which one of the following is expected after 100 generations?
- 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.
