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. Over the course of evolutionary time, what should occur?
A) Methylated DNA should become fixed in the gene pools of bacterial species.
B) Nonmethylated DNA should become fixed in the gene pools of bacteriophages.
C) Methylated DNA should become fixed in the gene pools of bacteriophages.
D) Methylated and nonmethylated strains should be maintained among both bacteria and bacteriophages, with ratios that vary over time.

Question

Quizplus · Accepted Answer

Over evolutionary time, both bacteria and bacteriophages will continue to adapt to each other's defenses. This will lead to the maintenance of both methylated and nonmethylated strains among both bacteria and bacteriophages. The ratios of methylated to nonmethylated strains will vary over time depending on the selection pressures present in the environment.

The Restriction Enzymes of Bacteria Protect the Bacteria from Successful