Tay-Sachs is inherited as an autosomal recessive allele. Homozygous individuals die within the first few years of life. However, there is some evidence that heterozygous individuals are more resistant to tuberculosis. Which of the following statements about Tay-Sachs is true?
A) The allele for Tay-Sachs is always selected against.
B) This situation is an example of heterozygote advantage if tuberculosis is present in a population.
C) This situation is an example of disruptive selection.
D) Heterozygotes will be more fit than either homozygote regardless of environmental conditions.

Question

Quizplus · Accepted Answer

Heterozygote advantage occurs when the heterozygous genotype has a higher fitness than either of the homozygous genotypes. In this case, heterozygous individuals have a higher resistance to tuberculosis, providing them with a selective advantage over homozygous individuals. However, this does not necessarily mean that the Tay-Sachs allele is always selected against, as heterozygotes can still pass on the allele to their offspring. The situation is not an example of disruptive selection, as there is not a clear distinction between two extreme phenotypes that are both advantageous in different environments. Finally, it is not accurate to say that heterozygotes will be more fit than either homozygote regardless of environmental conditions, as fitness is dependent on the selective pressures of the environment.

Tay-Sachs Is Inherited as an Autosomal Recessive Allele