Final answer:
The chance of siblings having the same MHC haplotype from heterozygous parents for each separate gene is 1/4, but for all three genes combined, it is 1/64. Given that none of the options provided match this, for a single gene the answer would be C. 1:4.
Step-by-step explanation:
The subject of this question is biology, specifically genetics. When considering parents who are heterozygous for their MHC haplotype, each parent has two different alleles for each gene, which they can pass on to their children. Since there are three highly polymorphic MHC I genes (HLA-A, HLA-B, and HLA-C), we need to calculate the probability for each gene separately and then combine the probabilities.
For each gene, a child can inherit one of two alleles from each parent, which gives us four possible combinations (A1A2, A1A3, A2A1, A2A3 where A1 and A2 are the alleles from one parent and A1 and A3 are the alleles from the other parent). Therefore, the chance that two siblings inherit the same allele pair from their parents for one MHC gene is 1/4. Since we need the same combination for all three genes, we have to multiply the probabilities: 1/4 (for HLA-A) × 1/4 (for HLA-B) × 1/4 (for HLA-C), which equals 1/64.
Given that none of the provided answer options match this calculation, the student may need to recheck the question or the options. However, if we only consider a single gene, the answer would be C. 1:4, since that is the chance for siblings to inherit the same allele pair for one MHC gene.