In: Biology
an isolated population of cats are observed for their frequency in an allele for striped and spotted coloring as well as the actual level of heterozygosity in each population. Allele frequency for stripes is 0.62 and spots 0.38, The observed frequency of heterozygotes is 0.08 What is the inbreeding coefficient of this population? is the population undergoing inbreeding based off of the inbreeding coefficient.
Consider the alleles for stripes and spots to be p and q respectively, with inbreeding occuring at a rate F.
Allele frequency for stripes (S) p = 0.62 Allele frequency for spots (s) q = 0.38
Genotype frequencies
Outbred | SS : p2 | Ss : 2pq | ss : q2 | outbreeding rate = 1-F |
Inbred |
SS : p p2 + Fpq |
2pq - 2Fpq |
ss : q q2 + Fpq |
inbreeding rate = F |
To calculate the inbreedingcoeeficient from the given genotype frequency of heterozygotes (Ss)
f(Ss) = 2pq - 2Fpq
f(Ss) = 2pq (1-F)
0.08 = 2 x 0.62 x 0.38 (1-F)
0.08 = 0.4712 (1-F)
0.08/ 0.4712 = 0.1697 = (1-F)
F = 1 - 0.1697
F = 0.8303
Therefore the inbreeding coefficient of the population is 0.83
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Whether the population is undergoing inbreeding can be understood in two ways
1) if the inbreeding coefficient is very high. 0.83 is a significantly high, which indicates that the population is undergoing inbreeding
2) Inbreeding leads to reduction in heterozygosity. Het = HetHW (1-F) where heterozygosity (Het) is reduced by a fraction F compared to the Hardy-Weinberg (HW) outbred expectation (HetHW = 2pq).
This is worked out earlier with the genotype frequency of the heterozygote (Ss) , i.e., f(Ss) = 2pq (1-F) = 0.08 .
0.08 is significantly low heterozygosity, which again indicates that the population is inbreeding.