Duchenne muscular dystrophy (DMD) is a sex-linked recessive disorder that results in a degenerative disease of the muscles of the body. As muscles gradually deteriorate, patients lose the ability to control the muscles and eventually die as breathing muscles are rendered useless. An extended family was studied over several generations and the incidence of DMD was followed as indicated in the pedigree below.
According to the pedigree, one can conclude that
- Jancy is at least a carrier of DMD
- Jancy has DMD
- Jancy docs not carry any copies of the DMD allele
- individual "D" will have two copies of the DMD allele
- individual "D" will not carry any copies of the DMD allele
Answer(s): A
Explanation:
Because Janey has had three children with DMD, she is at least a carrier of the disease. In particular, her son, individual "C" has the disease, so he must have gotten the disease allele from Janey, since his father could not have passed him an X chromosome.