H-W can then be used to show that p in the next generation will be the same as p in the survivors. When we add mutation into our equations, we end up with a steady state where selection balances mutation, and the deleterious recessive allele is maintained in the population. This implies that we should have a mutation rate of about 0.04 or 4 in 100. For alleles like this usually around 1 in 100,000 to 1 in 10,000. So mutation-selection balance is not likely.
Heterozygotes have an advantage over normal homozygotes.
The deadliest is Plasmodium falciparum . They are transmitted to humans by mosquitoes in the genus Anopheles . When a mosquito bites an infected individual, the parasites are taken up in the blood. They reproduce sexually in the gut of the mosquito, and work their way to the salivary glands. Once there they can be transmitted to the next human host.