Cyclin-dependent kinase inhibitor 1C (CDKN1C) is a paternally imprinted gene on
ID: 179657 • Letter: C
Question
Cyclin-dependent kinase inhibitor 1C (CDKN1C) is a paternally imprinted gene on chromosome 11. CDKN1C regulates cell proliferation. Individuals that have mutations in unimprinted CDKN1C are at higher risk of cancer. The pedigree below shows two individuals in the third generation with cancer because of inherited CDKN1C mutations. Assuming complete penetrance, which individual in generation 2 of the pedigree above is a carrier of the CDKN1C allele that led to cancer in generation 3. II.3 either II.3 or II.4 II.2 II.4Explanation / Answer
According to the question, the gene responsible for this disease is imprinted or carried on chromosome number 11. Since humans are diploid in nature, maximum two copies of this gene could be present on the chromosome at one time. It can be noticed from the pedigree that none of the individuals of second generation is affected from the disease, neither male not a female. However, the sudden appearance of individuals of third generation with this disease clearly demonstrates that:
Thus, it can be seen that both male and female of third generation are affected by this disease which means that the female contains a double set of these alleles. This holds true only if both the parents are heterozygous for this allele because only in that case a female offspring will carry two copies of these alleles from her parents and would get affected by the disease. Since the disease is paternally imprinted in humans, the male parent is indeed a carrier of this allele. Also, since 50% of their male and female offsprings are affected by the disease, the mother also ought to be a carrier i.e. XaX and XaY would give:
i.e. 50% male affected : 50% female affected
Thus, according to this explanation, choice 2 seems most correct.
Xa X Xa XaXa XaX Y XaY XYRelated Questions
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