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Free CLEP Science and Mathematics Exam Braindumps (page: 25)

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PDF with 494 Questions

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

  1. Jancy is at least a carrier of DMD
  2. Jancy has DMD
  3. Jancy docs not carry any copies of the DMD allele
  4. individual "D" will have two copies of the DMD allele
  5. 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.



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.


If Janey were homozygous recessive for DMD, what are the chances that she and Jimmy would have another child who has the disease?

  1. 0%
  2. 25%
  3. 50%
  4. 75%
  5. 100%

Answer(s): E

Explanation:

If Janey were homozygous recessive, all of Jimmy and Janey's children would receive X chromosomes carrying a DMD allele.



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.


Males are more likely to express the DMD allele than females because

  1. muscles are generally larger and stronger in males than in females
  2. males have two X chromosomes and can get twice as many DMD alleles
  3. males have only one X chromosome and if passed even one DMD allele, they will express it
  4. sex-linked traits are not expressed in females
  5. the DMD allele is carried on the Y chromosome

Answer(s): C

Explanation:

Males have only one X; therefore, if they get passed a defective X, they can only express those alleles. In contrast, females have two X's and can have a dominant, "normal" gene to override a defective one (e.g., one for DMD) on their other X.



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.


How many generations of family are represented on the pedigree shown?

  1. 3
  2. 4
  3. 5
  4. 6
  5. 12

Answer(s): B

Explanation:

Each level of the pedigree is one generation. John and his wife are the parents of child "B" and another girl, while Jimmy and Janey are the grandchildren of John and his wife, and individuals on the row with "C" and "D" are the great-grandchildren.






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