Recall that the equation for the relative fitness of an individual is
where n1 is the number of heterozygous mutations in the individual, n2 is the number of homozygous mutant loci, and nf is the number of fixed mutations in the population. We can factor this into two parts: the effects due to segregating loci, and the effects of fixed loci:
where
and
One way to interpret this new equation is that of all the
individuals that fail to survive, 
die as a result
of too many segregating mutations, and 
die from
fixed mutations. The significance of this observation is
that the individuals that die from fixed mutations are going
to do so no matter how many segregating mutations they carry;
in other words, it is not even necessary to go through the
steps of drawing random parents, combining genes, and counting
mutations.
