AP-Micro Microbiology: Microbial Genetics 3

Question 1

Bacteriophage lambda can undergo lysogeny by integrating into the host genome as a prophage. Which viral protein is primarily responsible for this integration?

Accepted Answer

Integrase (Int)

Answer

Lambda integrase (Int) catalyzes site-specific recombination between the phage attP site and the bacterial attB site to insert the prophage.

Question 2

In generalized transduction, which type of bacteriophage can transfer any portion of the host chromosome?

Accepted Answer

Virulent phages that package host DNA randomly

Answer

In generalized transduction, during lytic infection some phage heads accidentally package random fragments of host DNA instead of phage DNA, allowing any gene to be transferred.

Question 3

What is the function of the recA gene product in E. coli?

Accepted Answer

It catalyzes strand exchange during homologous recombination and activates SOS response

Answer

RecA protein binds single-stranded DNA, facilitates homologous strand exchange during recombination, and acts as a coprotease to induce the SOS response.

Question 4

A transposable element that requires an RNA intermediate for movement is called a:

Accepted Answer

Retrotransposon

Answer

Retrotransposons transpose via an RNA intermediate that is reverse-transcribed into DNA before integration, similar to the replication cycle of retroviruses.

Question 5

In the lac operon, what happens in the presence of glucose and absence of lactose?

Accepted Answer

The operon is repressed by the lac repressor and CAP is inactive

Answer

When glucose is present, cAMP levels are low so CAP cannot activate transcription; when lactose is absent, the lac repressor binds the operator, doubly repressing the operon.

AP Practice Test

AP Practice Test

AP-Micro Microbiology: Microbial Genetics 3