Question: Normal German Shepherd dogs possess a thick coat of hair. The gene responsible for this normal co…

Normal German Shepherd dogs possess a thick coat of hair. The
gene responsible for this normal coat (the H gene) is cut by EcoRI
into three restriction fragments:0.4, 0.7and 0.9 Kb in size, each
of which is capable of hybridizing with a radioactive probe
produced from the cloned H gene. A dog breeder was shocked to
discover that his newly acquired normal-haired male and female
German Shepherds produced both hairless and normal-haired puppies
when mated. (About 25% of the puppies in the litter lacked hair.)
DNA was extracted from skin samples obtained from the hairless
puppies, from their normal littermates and from the parents of the
puppies. The DNA samples were digested with Eco RI and Southern
blotted using the H gene as a probe. It was found that the DNA
samples from puppies produced three different patterns of bands.
(1) All (3) of the hairless puppies: 0.9 and 1.1 kb. (2) Three of
the normal-haired puppies: 0.4, 0.7 and 0.9 Kb. (3) Six of the
normal haired puppies: 0.4, 0.7, 0.9 and 1.1 Kb. a) Draw a diagram
of the restriction map of the normal H gene. b) Draw a restriction
map that explains the occurrence of the hairless puppies. c) If the
parents DNA was subjected to this analysis which of the three
possible patterns would you expect to see. d) If you crossed a
puppy with the 0.4, 0.7 and 0.9 Kb band pattern with a puppy with
the 0.9 and 1.1 kb band pattern, what percentage of the offspring
would be normal?