Restriction Enzymes in Bacteria Protect the Bacteria from Successful Attack

Multiple Choice

Restriction enzymes in 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, they in turn select for bacteria whose genomes are not methylated and whose restriction enzymes instead degrade methylated DNA. Which of the following factors is most likely to cause the changes?

A) frequency-dependent selection
B) evolutionary imbalance
C) heterozygote advantage
D) neutral variation