Virulence and the Mechanisms of Gene Regulation I

Question 1

Describe how gene regulation contributes to infection/disease

Answer 1

It enables pathogens to adapt to changes in their environment

If they want to be effective invaders they must rapidly express a variety of gene products

Question 2

Virulence factor

Answer 2

Bacterial property required for entry, growth, or survival in the host

(capsule, surface proteins, adhesins, acid shock proteins,, etc)

Question 3

Virulence gene

Answer 3

A gene that encodes a virulence, lostt of such gene decreases virulence

Often located on plasmids (mobile genetic elements) or pathogenicity islands (localized regions of chromosome)

Question 4

Pathogenicity Islands

Answer 4

Large, localized regions of the chromosome

Often absent in closely related non-pathogenic strains

Question 5

Describe the organization of a typical operon

Answer 5

Includes a promoter, operator, cistrons, and terminator

Question 6

Describe the process of transcription

Answer 6

RNApolymerase recognizes and binds (primarily its sigma unit) to the promoter region of the DNA. The RNAP/DNA interaction is a closed complex

Once bound, RNAP causes double stranded DNA to open (open complex)

Strand separation allows synthesis of mRNA strand complementary to DNA sense strand

Transcription proceeds, elongating the mRNA until RNAP encounters a termination signal

Question 7

Describe the regulation of transcription initiation

Answer 7

The repressor binds at the operator which prevents binding of RNAP to the promoter (steric hindrance)

Inducer is a small molecule that binds the repressor and changes it conformation so it can no longer bind DNA

The activator interacts with RNAP, increasing the ability of RNAP to bind the promoter

Question 8

Define “regulon”

Answer 8

A group of operons subject to the control of a common regulator