Final answer:
The frequency of B1B1 individuals in the population is calculated by dividing the number of B1B1 individuals (20) by the total number of individuals (70), resulting in approximately 28.5% or option 3.
Step-by-step explanation:
To answer the question about the frequency of B1B1 individuals in a population, we first need to know the total number of individuals in the population. The total is found by adding up all the individuals with different genotypes: 20 B1B1 individuals, 35 B1B2 individuals, and 15 B2B2 individuals. Therefore, the total number of individuals is 20 + 35 + 15, which equals 70.
Next, to find the frequency of B1B1, we divide the number of B1B1 individuals by the total number of individuals in the population:
Frequency of B1B1 = Number of B1B1 individuals / Total number of individuals = 20 / 70 ≈ 0.2857 or 28.57%
This means that the frequency of B1B1 individuals is approximately 28.5%, which corresponds to option 3) 28.5.