So let's say I have a tetraploid species and I have 4 possible alleles for a particular locus. I have found that I can have 35 total possible genotypes and I know the allele frequencies for each of the 4 alleles, that I will randomly set as $$F_a = 0.2, F_b = 0.3, F_c = 0.4, F_d=0.1$$ for the sake of the example.
However, I am having a hard time wrapping my mind around how to calculate the number of occurrences of a particular genotype, $abc$, in a population of 1000 people.
I understand the allele frequencies, for instance, in the population of 1000 people, given all 1000 observed genotypes, 40% of them had allele $c$. But these are individual values and I have no information on how likely they are to be linked. (I am supposed to assume HW principle holds, but not sure how this helps).
How do I calculate the number of occurrences of the genotype $abc$ in the population?