The formation of genes is also probabilistic

Imagine that a boat capsizes,and 10 survivors swim to shore on a deserted island. They are never rescued,and they form a new population that exists for thousands of years.Strangely enough,five of the survivors have red hair.Red hair is created when a person inherits two copies of the red gene from their parents.
If you only have one copy of the gene,you won't have red hair.To make this easier, we will assume that the five non-redheads are not carriers of the gene.
The initial frequency of the red-hair gene is therefore 50 percent, or 10 of 20 total genes.