Your aunt moves out of the town and leaves you her mouse, Henry. In order to make some money, you decide to breed mouse and sell the offspring. In looking over Henry's family history, you discover that Henry's grandfather expressed a rare genetic disorder which leads to brittle bones. This disorder is hereditary and is regulated by recessive allele b. Based on this information, you realize that there is a possibility that Henry could be heterogeneous for the allele. If this is the case, the genetic condition may passed to his offspring.

Question

Your aunt moves out of the town and leaves you her mouse, Henry. In order to make some money, you decide to breed mouse and sell the offspring. In looking over Henry's family history, you discover that Henry's grandfather expressed a rare genetic disorder which leads to brittle bones. This disorder is hereditary and is regulated by recessive allele b. Based on this information, you realize that there is a possibility that Henry could be heterogeneous for the allele. If this is the case, the genetic condition may passed to his offspring.

1) What method could you use to determine if Henry is heterogeneous and carries the recessive allele b?
2) Using the method you described in Q1, determine the expected phenotype and genotypes of all individuals if Henry is heterogeneous or if he is homozygous dominant.

Answer 1

1) In order to determine if Henry is heterozygous and carries the recessive allele b, you can perform a test cross. A test cross involves breeding Henry with a known homozygous recessive individual. By examining the offspring, you can determine if Henry carries the recessive allele b.

2) If Henry is heterozygous and carries the recessive allele b, the expected phenotype and genotypes of the offspring would depend on the genotype of the other parent. If the other parent is homozygous recessive (bb), all the offspring will be carriers of the recessive allele (Bb) but will not express the genetic disorder. If the other parent is heterozygous (Bb), there would be a 50% chance of the offspring being carriers (Bb) and a 50% chance of them being homozygous dominant (BB) and not carrying the recessive allele.

On the other hand, if Henry is homozygous dominant (BB), all the offspring will be heterozygous (Bb) and carriers of the recessive allele but will not express the disorder.