AP BIOLOGY

EVOLUTION

EVOLUTION OF A POPULATION

Question [CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
Within a population of 500 butterflies, the color purple is dominant over the color white. 200 of the butterflies are white. What is the frequency of homozygous dominant individuals? Give your answer as a decimal to the nearest hundredth.
A
.40
B
.36
C
.16
D
.60
Explanation: 

Detailed explanation-1: -In a population that is in Hardy-Weinberg equilibrium, the frequency of homozygous dominant individuals is 0.36.

Detailed explanation-2: -Calculate the percentage of individuals homozygous for the dominant allele. We know that the frequency of the recessive homozygote genotype is q2 and equal to 0.09. Thus, p = 1 – q ∴ p = 1 – 0.30 = 0.70 ∴The homozygote dominants are represented by p2 = (0.70)2 = 0.49 or 49% Page 2 4.

Detailed explanation-3: -The frequency of heterozygous individuals. Answer: The frequency of heterozygous individuals is equal to 2pq. In this case, 2pq equals 0.32, which means that the frequency of individuals heterozygous for this gene is equal to 32% (i.e. 2 (0.8)(0.2) = 0.32).

Detailed explanation-4: -The frequency of homozygous dominant plants (p2) is (0.6)2 = 0.36. Out of 100 individuals, there are 36 homozygous dominant (YY) plants. The frequency of heterozygous plants (2pq) is 2(0.6)(0.4) = 0.48. Therefore, 48 out of 100 plants are heterozygous yellow (Yy).

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