In a natural selection, the frequency of an allele not necessarily increases always. The frequency of an allele decreases sometimes in natural selection. There are different modes of natural selection –
a) Mutation – When a new allele is created
b) Random mating
c) Random fertilization
d) Recombination
A common example of natural selection in which the genetic variation decreases is known as founder effect in which the population starts ascending from a small population.
Coronary artery disease is when plaque in arteries causes blood to not flow correctly or as smoothly as possible. Therefore, a heart attack can occur if blood can't flow.
