Answer to Question #350560 in Genetics for NCCN

Question

In foxes, a pair of alleles, Q and q, interact as follows:  QQ will cause the fox to die at the embryonic stage; Qq produces platinum coloured fur, and qq produces silver foxes. Could a fox breeder produce silver foxes without having some foxes that would die?  Prove your answer by showing the full genetic cross (5 steps) and giving a word explanation at the end.

Answer 1

1. Q -the platinum fur allele, q - the silver fur allele.
2. QQ - the lethal phenotype, Qq - platinum coat, qq - silver coat.
3. A breeder's goal to produce only silver foxes (qq) can be achieved by crossing silver foxes. Each of the parent organisms (silver fox, qq) produces only one type of gamete, so only silver offsping are expected.
4.  Parents: qq x qq

Gametes: q

Offspring: qq 

5.Only the crossing of the silver foxes (recessive homozygotes, qq) will give exclusively silver offspring without any lethality among the offspring.