Dolly is a 2-1/2-year-old Golden Retriever.  She used to belong to a breeder.  In her first litter she had 5 puppies, 2 males and 3 females.  One of the males died before weaning and the other was returned by the purchaser at age 4 months, due to exercise intolerance, weakness and abnormal muscle development, and splaying of distal limbs.  This pup showed marked increases in the levels of creatine kinase (CK), aspartate aminotransferase (AST), and alanine aminotransferase (ALT).  The pup’s problems worsened and he was euthanized at 7 months; necropsy showed megaesophagus and a muscle biopsy showed a complete absence of labeling for the protein dystrophin.  The diagnosis in this pup was X-linked muscular dystrophy.

The breeder immediately had Dolly spayed and placed her in a  rescue program; as a perfectly healthy, calm and biddable dog, eager to please, she was adopted one day later by an elderly couple who have found her to be a joy. 

Points to ponder:

1.  What subcellular organelle(s) and structures are involved in the development of the two males’ problems?

2.  Why is the negative result of immunostaining for dystrophin definitive?

3. Why isn’t Dolly sick?

4. What is the breeder’s responsibility to the buyers of the female puppies?