Question

A population of cats has the following genotypes for an X-linked coat-color trait (O for the dominant brown allele, o for the recessive orange allele):

Brown homozygous females: 30
Brown heterozygous females: 75
Orange females: 10
Brown males: 50
Orange males: 65
What are the allele frequencies in this population?
a)O = 0.54, o = 0.46
b)O = 0.59, o = 0.41
c)O = 0.51, o = 0.49
d)O = 0.43, o = 0.57
e)O = 0.40, o = 0.35

Answer 1

The allele frequencies for the X-linked coat-color trait in a population of cats are calculated based on the total number of alleles from both males and females. The frequency of allele O is approximately 0.54 and allele o is approximately 0.46, corresponding to option (a).

Step-by-step explanation:

To determine the allele frequencies in the cat population for the X-linked coat-color trait, we first calculate the total number of alleles in the population. Recall that males have one X chromosome and females have two. Each male has one allele for the trait, and each female has two alleles.

For the females:

• Brown homozygous (OO): 30 females = 60 O alleles
• Brown heterozygous (Oo): 75 females = 75 O and 75 o alleles
• Orange (oo): 10 females = 20 o alleles

For the males:

• Brown (O): 50 males = 50 O alleles
• Orange (o): 65 males = 65 o alleles

Adding these together gives:

• O alleles: 60 + 75 + 50 = 185
• o alleles: 75 + 20 + 65 = 160

Total alleles in the population = O alleles + o alleles = 185 + 160 = 345 alleles

To find the frequencies:

• Frequency of O = Number of O alleles / Total alleles = 185 / 345 ≈ 0.536
• Frequency of o = Number of o alleles / Total alleles = 160 / 345 ≈ 0.464

Therefore, the allele frequencies are approximately O = 0.54 and o = 0.46, which corresponds to option (a).