Stalk height in sunflowers is determined by two alleles at a locus, T and t, which display incomplete dominance. TT individuals are tall, Tt are medium, and tt are short. In a population that is in Hardy-Weinberg equilibrium, we count 1,546 short plants out of 9,666. How many plants do you expect to be tall?

Question

Quizplus · Accepted Answer

We can use the Hardy-Weinberg equation to solve the problem:
p^2 + 2pq + q^2 = 1
where p is the frequency of the T allele and q is the frequency of the t allele in the population.
From the problem, we know that:
q^2 = 1,546/9,666 
q^2 = 0.160
q = 0.4 (because this is a case of incomplete dominance, we cannot assume q is equal to 0.2)
Using the fact that p + q = 1 and q = 0.4, we can find that p = 0.6.
To find the expected frequency of tall plants, we can use the equation:
p^2 = (0.6)^2 = 0.36
Finally, we can multiple the expected frequency by the total number of plants:
0.36 x 9,666 = 3,480
Therefore, the answer is C) 3,480.

Stalk Height in Sunflowers Is Determined by Two Alleles at a Locus