Final answer:
To find the frequency of allele a among 600 horses, we consider the homozygous recessive and heterozygous individuals, tally the a alleles they contribute, and divide by the total number of alleles in the population.
The calculation reveals that the frequency of allele a is 0.25, while the frequency of allele A is 0.75.
Step-by-step explanation:
To calculate the frequency of allele a in a population of horses, we must first understand the concept of alleles and allele frequencies. In this case, allele a is one of two alleles at a particular locus involved in immune response.
Since we have two alleles (A and a) in a diploid organism like a horse, each individual has two copies of the gene, one from each parent.
According to the question, the population consists of 600 horses, with 70 individuals being homozygous recessive (aa) and 160 being heterozygous (Aa). To find the frequency of allele a (represented here as 'q'), we need to use the formula q = number of a alleles/total number of alleles.
Since aa individuals contribute two a alleles each, and Aa individuals contribute one, the calculation will be as follows:
Number of a alleles from aa individuals = 70 * 2 = 140
Number of a alleles from Aa individuals = 160 * 1 = 160
Total number of a alleles = 140 + 160 = 300
Now, given that each horse has two alleles, the total number of alleles in the population will be 600 * 2 = 1200.
Hence, the frequency of allele a (q) is calculated as: q = 300/1200 = 0.25.
Remember that the frequency of allele A (p) and the frequency of allele a (q) must add up to 1, so we can now also calculate p as p = 1 - q = 1 - 0.25 = 0.75.
The frequency of the dominant allele A in this population of horses is therefore 0.75.