Question

Which of the following leads to the higher frequency of inherited Becker muscular dystrophy compared to Duchenne muscular dystrophy?

A Higher fitness of mutations in males affected with Becker than Duchenne muscular dystrophy
B Higher mutation rate for Duchenne-associated disease
C Increased frequency of prenatal termination for Duchenne cases
D Lower penetrance in female carriers for Becker versus Duchenne mutations
E None of the above

Answer 1

The higher frequency of inherited Becker muscular dystrophy compared to Duchenne muscular dystrophy is likely due to the increased frequency of prenatal termination for Duchenne cases since it is more severe and has earlier onset than Becker muscular dystrophy. Both disorders are X-linked recessive so male offspring are more likely to be affected while female offspring are more likely to be carriers.

Step-by-step explanation:

The question pertaining to Becker muscular dystrophy compared to Duchenne muscular dystrophy involves understanding the inheritance patterns of these diseases. Duchenne muscular dystrophy (DMD) is an X-linked recessive disorder, which typically affects males due to having one X chromosome. Female offspring have a second X chromosome that can compensate for the defective gene, making them carriers without often being affected.

Based on the inheritance patterns, the correct answer to the question would be 'C Increased frequency of prenatal termination for Duchenne cases,' given that prenatal diagnosis may lead to a higher frequency of prenatal termination for Duchenne due to its more severe symptoms compared to Becker muscular dystrophy.

It's important to note that female offspring have a 50% chance of being carriers when the mother is a carrier, while male offspring have a 50% chance of being affected with the disease because they inherit only one X chromosome from the mother. This inheritance pattern is characteristic of X-linked recessive diseases.