Question

What genetic force leads to the variability in the percentage of mutant mtDNA molecules that are present in the children of a mother who exhibits heteroplasmy for the mutation?

A Positive selection
B Negative selection
C Genetic bottleneck
D Reduced fitness
E Balancing selection

Answer 1

The variability in the percentage of mutant mtDNA molecules that affects the children of a mother with heteroplasmy is due to a genetic bottleneck, which is when only a subset of the mother's mitochondria are passed on, causing a random fluctuation in the proportion of mutant mtDNA.

Step-by-step explanation:

The genetic force that leads to the variability in the percentage of mutant mtDNA molecules present in the children of a mother exhibiting heteroplasmy for the mutation is C. Genetic bottleneck. This occurs because during the process of transmitting the mitochondria from mother to offspring, only a subset of the mother's mitochondria are passed on. This can lead to a random fluctuation in the proportion of mutant to normal mtDNA, resulting in variable expression of mtDNA mutations among offspring, which is a hallmark of a genetic bottleneck phenomenon. Factors such as genetic drift, in which some individuals in a lineage reproduce more than others due to chance, and allelic variation influencing phenotype, can also impact the frequency of alleles—including those involved in mtDNA mutations.