Question

Homologous recombination occurs in a heterozygote in which alleles D and d differ by a single base pair. The D allele has a G (a GC base pair) at one position, whereas the d allele has a C (a CG base pair) at the same position. If branch migration causes heteroduplex formation across this position, what is the expected outcome?
a. Both D and d alleles will remain unchanged because G can base pair with C.
b. Mismatch repair will identify abnormal G-G and C-C base pairs and may convert the D allele to a d allele or the d allele to a D allele.
c. Mismatches will cause the Holliday junction to be unstable and to resolve by the noncrossover pathway.
d. Mismatch repair will identify abnormal G-G and C-C base pairs and gene conversion will always occur in situations like this one when mismatched bases exist within the heteroduplex region.
e. Mismatch repair will identify an abnormal C-G base pair and will ensure that the cell has two copies of each allele.

Answer 1

Answer:

b. Mismatch repair will identify abnormal G-G and C-C base pairs and may convert the D allele to a d allele or the d allele to a D allele.

Explanation:

The expected outcome if branch migration occurs is that mismatch repair will identify abnormal G-G and C-C base pairs and may convert the D allele to a d allele or the d allele to a D allele.