Final answer:
Without the genotype frequencies for allele 13, it is not possible to accurately determine the probability of it being present in a randomly selected individual.
Step-by-step explanation:
The probability of allele 13 being present in a randomly selected individual, p(13), can be calculated using the Hardy-Weinberg equation. However, without the genotype frequencies for allele 13, it is not possible to accurately determine the probability. The Hardy-Weinberg equation states that p^2 + 2pq + q^2 = 1, where p and q are the frequencies of the two alleles. In this case, allele 13 could be represented by p or q depending on its frequency in the population. Without that information, we cannot calculate the probability.