Patterns
of Genetic Inheritance—
Dominant
Inheritance
Dominant inheritance accounts for about 15-20% of genetic deafness. Here, the deafness gene is the dominant gene, and the hearing gene is the recessive gene. Therefore, only one copy of the deafness gene is required for a person to be deaf.
People with a dominant form of genetic deafness usually have a deaf parent. The chance that subsequent children will be deaf can be as high as 1/2 or 50%. However, some dominant genes may not be fully expressed in people who have the deafness gene. This phenomenon is referred to as reduced penetrance. Therefore, some deaf individuals may inherit a dominant gene for deafness from one of their parents even though that parent is not deaf.
Similarly, the hearing brothers and sisters of a child with dominant
deafness can sometimes carry the gene without being deaf, but they might
have deaf children. In these cases, one might say that deafness has
“skipped a generation.”
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page—X-Linked Inheritance