Question

Question : The CDKN1C gene is a maternally imprinted gene that is important for fetal development. Mice that are homozygous null for CDKN1C, meaning no expression of the CDKN1C gene, have an overgrowth phenotype during fetal development and are large.

a. ) A female mouse is heterozygous for a null allele of the CDKN1C gene. The null allele was inherited from her paternal parent and the allele inherited from her maternal parent is the wildtype DNA sequence of the CDKN1C gene. What is the phenotype of this female mouse?

A. small (mutant phenotype)

B. normal size (wildtype phenotype)

C. large (mutant phenotype)

D. Can not be determined

b.)  The female mouse described in question 6 mates with a male mouse that is heterozygous for a null allele of the CDKN1C gene (the other allele is wildtype). What are the expected phenotypes of their progeny?

A. All large progeny

B. All wildtype progeny

C. 25% large progeny and 75% wildtype progeny

D. 50% large progeny and 50% wildtype progeny

E. 75% large progeny and 25% wildtype progeny

F. all large males and all wildtype females

G. all wildtype males and all large females

Answer 1

a) maternally imprinted gene means the allele from the mother is not expressed in the progeny, here the maternal allele s normal and the paternal allele is null mutant so the phenotype of the mice will be C. large (mutant phenotype)

b) the female mice is heterozygous and she is mated with a male heterozygous at the locus, the allele from the mother is not expressed in the progeny the male is heterozygous so 50% of his progeny will inherit normal allele from him and 50% will inherit mutated allele from him so 50% of the progenies are large and 50% of the progenies are normal so the answer is D. 50% large progeny and 50% wildtype progeny