You are studying a population of cactus and you discover tha

You are studying a population of cactus and you discover that there are two spine lengths (short and long) that follow Mendelian inheritance patterns. Breeding data suggest that the long-spine allele (LS) is dominant to the short-spine allele (SS), and when you examine plants from your wild population you find 168 plants (out of 200) with the long-spine phenotype. Based on this, what would you expect to be the frequency of the SS allele? 16% 40% 50% 60% 84%

Solution

The answer is 40%.

For explanation

Apply Hardywein berg law for freequency calculation

HardyWeinberg law = (a+b)^2 = a^2+2ab+b^2= 1

Frequency of long sprine population = 200 – 168 = 32
The feequncy of ss ss = 32/200 = 0.16
ss = sqrt(0.32) = 0.4
ls = 1-ss = 1-0.4 = 0.6

The frequency of populations
Ls ls = 0.6 x 0.6 = 0.36 x 200 = 72
Ls ss = 2 x 0.6 x 0.4 = 0.48 x 200 = 96
Ss ss = 0.4 x 0.4 = 0.16 x 200 = 32

The frequency of ss allele = (32+32+96)/400 = 40%