What is the Function of the Cos Sites in the

Question

What is the function of the cos sites in the  λ phage genome?
A) They function as the origin of DNA replication
B) They bind to the cI repressor
C) They bind to the N antiterminator
D) They circularize the genome
E) They are the sites of integration with the host chromosome

Accepted Answer

The cos sites (short for cohesive ends sites) play a crucial role in the circularization of the λ phage genome. Each cos site has complementary sequence regions that can base pair with each other, leading to the formation of a circular DNA molecule. The circularization is important for efficient packaging of the phage DNA into the preformed phage head during the viral assembly process.