The restriction enzymes of bacteria protect the bacteria from successful attack by bacteriophages, whose genomes can be degraded by the restriction enzymes. The bacterial genomes are not vulnerable to these restriction enzymes because bacterial DNA is methylated. This situation selects for bacteriophages whose genomes are also methylated. As new strains of resistant bacteriophages become more prevalent, this in turn selects for bacteria whose genomes are not methylated and whose restriction enzymes instead degrade methylated DNA. The outcome of the conflict between bacteria and bacteriophages at any point in time results from ________.
A) frequency-dependent selection
B) evolutionary imbalance
C) heterozygote advantage
D) neutral variation

Question

Quizplus · Accepted Answer

The outcome of the conflict between bacteria and bacteriophages at any point in time results from frequency-dependent selection. As new strains of resistant bacteriophages become more prevalent, this selects for bacteria with non-methylated genomes and restriction enzymes that can degrade methylated DNA. This, in turn, selects for bacteriophages whose genomes are also methylated. This cycle of selection leads to fluctuations in the frequency of the different genotypes within the population, based on their interactions with each other.

The Restriction Enzymes of Bacteria Protect the Bacteria from Successful