The plant Arabidopsis thaliana routinely self-pollinates in natural populations.
ID: 77877 • Letter: T
Question
The plant Arabidopsis thaliana routinely self-pollinates in natural populations. Researchers have estimated the level of inbreeding at F = 0.36 by genotyping individuals for the Dfy locus, which has two alleles: Dfy-A and Dfy-B. One isolated population in an alpine meadow has 120 individuals in it and a Dfy-B allele frequency of 0.3. A) Calculate the number of heterozygotes expected in this population. B) How many heterozygotes would be expected in this population if the plants did not self pollinate?Explanation / Answer
For an inbred population
Frequency of homozygotes (AA)=p2 +Fpq, where F is ithe inbreeding coefficient.
Frequency of heterozygotes (AB)= 2pq(1-F)
Frequency of homozygotes (BB)= q2 +Fpq
IInbreeding does not change allele frequency but it can change genotype frequency. Inbreeding causes an increase in homozygosity and decreases heterozygosity.
Allele frequency of B, q=0.3
So p=1-q=1-0.3=0.7; p= 0.7
F of heterozygotes (AB)= 2pq(1-F)= 2 x 0.7 x0.3(1-0.36)
f(AB)= 0.269
A). So number of heterozygotes expected in this population=0.269 x 120= 32.26
B) If the plants did not self pollinate, then
frequency of heterozygotes (AB) is given by 2pq= 2 x 0.7 x 0.3= 0.42
So number of heterozygotes when there is no self pollination= 0.42 x 120= 50.4
As can be seen from the answers in A and B, inbreeding decreases heterozygosity.