Patterns
of Genetic Inheritance—
Recessive
Inheritance
Recessive inheritance is the most common form of genetic deafness, accounting for approximately 80% of inherited deafness. Parents may wonder how their child can have a genetic form of inheritance if they are both hearing. The reason is that each of these parents has one dominant hearing gene and one recessive deafness gene. Even though they are hearing, they are both carriers of a recessive gene for deafness.
The deaf child has inherited a “double dose” of the deafness gene, one
from each parent. With recessive inheritance, the chance that each
subsequent child born to the carrier parents will be deaf is 1/4 or 25%
because there is a 50% chance that the gene for deafness will be transmitted
by both the mother and the father (1/2 x 1/2 = 1/4).
next
page—Dominant Inheritance