Mendelian Genetics Problem Set

1. A cattle rancher discovers that one of his bulls has a great deal of muscle mass but little fat, and wishes to create a pure-breeding stock with that trait. When he breeds the bull with wild-type cows, all of the offspring are wild-type. How can the rancher create his pure stock if the allele for lean muscle is autosomal?

2. The same cattle rancher has a bull that is unusually docile and wishes to create a pure-breeding stock with that trait. When he breeds the bull with wild-type cows, all of the calves are wild-type. How can the rancher create his pure stock if the allele for tameness is sex-linked?

3. A woman with AB blood type marries a man who has type A.
--What are all the possible blood genotypes that their children could have? Remember that you don't know if he is AA or AO.
--How could you find out his genotype by:
a. Studying their children's blood phenotypes?
b. Studying his (the father's) ancestors' blood phenotypes?

4. A scientist notices that the fish that she is studying come in 3 colors. when she breeds two yellow fish, all of the offspring are yellow. When she breeds two blue fish, all of the offspring are blue. when two green fish are bred, 25% of the offspring are yellow, 25% are blue, and the rest are green.
--How would you describe the alleles for color in these fish?
--What would result if you bred a yellow fish with a blue fish?
--How about a green with a blue?

5. An enterprising pet store owner is attempting to create a pure strain of ultra-dwarf mice to sell as novelty pets. he breeds 10 pairs of ultra-dwarf mice and counts the different phenotypes seen in the offspring. (A wild-type mouse litter is 10 mice.) In the F1 generation, 50 are ultra-dwarf, and 25 are wild-type. Each time he breeds two ultra-dwarves he gets the same ratio.
--What is going on?
--Will he ever get a pure strain? If not, why?