In this example for the offspring between **first cousins**, first measure the probability that she
will be homozygous for the recessive **allele a** inherited from her great-grandmother.

Each generation has a **1/2** probability of inheriting the ** a allele**.

The probability that all **6** inheritances contain the ** a allele** is
(

Since she can also be homozygous for any of the other 3 alleles in her great-grandparents,
**F** = 4 x (**1/64**) = **1/16**.