To determine the number of copies of a specific allele on the Y chromosome within a population, follow these steps:

Identify Relevant Population Subset

Since the allele is located on the non-recombining region of the Y chromosome, it is only present in males. The Y chromosome is passed directly from father to son.

Calculate Number of Males

Given the total population size is N and the sex ratio is 1:1, the proportion of males in the population is approximately 1/2. Therefore, the number of males is:

$ \text{Number of Males} = \frac{N}{2} $

Determine Total Y Chromosome Alleles

Each male individual carries one Y chromosome. Thus, the total number of Y chromosomes (and consequently, the total number of alleles at a given Y-linked locus) in the population is equal to the number of males.

$ \text{Total Y Alleles} = \text{Number of Males} = \frac{N}{2} $

Calculate Allele Copies

The allele frequency represents the proportion of a specific allele among all alleles at that locus. To find the number of copies of this specific allele, multiply its frequency by the total number of Y-linked alleles in the population.

$ \text{Number of Allele Copies} = (\text{Allele Frequency}) \times (\text{Total Y Alleles}) $

Substituting the given values:

$ \text{Number of Allele Copies} = 0.3 \times \frac{N}{2} = \frac{0.3 N}{2} $

Therefore, the number of copies of the allele in the population is $ \frac{0.3 N}{2} $.