Question

Which one of the following statements best describes antagonistic pleiotropy?

1) The net fitness of an allele experiencing antagonistic pleiotropy may depend on the environment
2) Alleles experiencing antagonistic pleiotropy should always be strongly selected against
3) Antagonistic pleiotropy results when a gene influences more than one characteristic/phenotypic trait
4) None of the above

Answer 1

Antagonistic pleiotropy is best described as a situation where an allele may have both beneficial and detrimental effects depending on the environment, which influences the allele's net fitness and frequency in the population.

Step-by-step explanation:

The best statement that describes antagonistic pleiotropy is that the net fitness of an allele experiencing antagonistic pleiotropy may depend on the environment. This is confirmed by the scenario with the sickle cell trait (allele 'S'), which exhibits a heterozygote advantage in malaria-endemic regions but would not confer the same benefit where malaria is absent. In the absence of malaria, the fitness costs associated with having at least one 'S' allele (such as susceptibility to sickle cell anemia) would likely lead to a decrease in its frequency.

Similarly, a dominant mutant allele may exert different effects on the organism's phenotype depending on environmental factors. Antagonistic pleiotropy is a phenomenon where a gene influences multiple phenotypic traits. It is a form of genetic trade-off where an allele has positive effects on one trait but negative effects on another. The net fitness of an allele experiencing antagonistic pleiotropy may depend on the environment, so statement 1 is the best description of antagonistic pleiotropy.