microbial genetics 3

Question 1

Bacterial chromosome

Answer 1

Single, large circular DNA molecule

~1-6 megabases

Question 2

Plasmid

Answer 2

Small, circular DNA molecule

Separate from bacterial chromosome, but replicated and transferred to daughter cells

Question 3

Bacterial genome characteristics

Answer 3

Small
1 chromosome

Haploid

No exons/introns/histones

Transcription/translation are coupled

Question 4

Polycistronic mRNA

Answer 4

An mRNA molecule that contains information from multiple genes by a single promoter

Question 5

Bacterial gene repression

Answer 5

A repressor binds to the operator of the gene, and transcription will not occur
Regulators can bind to the repressor, removing it and allowing transcription

Question 6

Bacterial positive gene regulation

Answer 6

Low affinity RNA polymerase may require an activator binding to the gene before the polymerase can bind

Question 7

Bacterial vertical gene transfer

Answer 7

Genes are passed to progeny of bacteria

Question 8

Bacterial horizontal gene transfer

Answer 8

Genes are passed from one bacteria to another bacteria

Question 9

Methods of bacterial horizontal gene transfer

Answer 9

Transformation
Conjugation

Transduction

Question 10

Evolution of bacteria

Answer 10

Unassisted, bacteria would adapt incredibly slowly

DNA repair is good

Question 11

How is bacterial evolution enhanced?

Answer 11

The development of horizontal gene transfer

New virulence factors can be developed through this process

Question 12

Homologous recombination

Answer 12

Exchange of DNA between two DNA molecules based on homology

Mediated by RecA

Question 13

Transformation

Answer 13

Uptake of free DNA from environment

Question 14

Process of transformation

Answer 14

DNA is released into environment (bacterial death) - this DNA is not protected
DNA is actively imported into bacterial cells

Homologous recombination

Question 15

Conjugation

Answer 15

DNA transfer directly from one bacterial cell to another via cell contact

Question 16

Process of conjugation

Answer 16

Fertility factor (F-Factor)
Sex pilus formation

DNA transferred from donor to recipient bacterium - homologous recombination

Question 17

F-Factor

Answer 17

Carries genes, tra operon, and oriT

Question 18

Tra operon

Answer 18

Encodes the sex pilus

Question 19

Sex pilus

Answer 19

Bridge that allows the transfer of genetic information from one cell to another

Question 20

OriT

Answer 20

Origin of transfer

Where a single strand break occurs for transfer

Question 21

Recipient bacterium

Answer 21

Must be F- (no F-Factor) or cannot receive information from sex pilus

Question 22

F+ x F- conjugation

Answer 22

F- -> F+
Only a single strand is transferred, no bacterial genes are transferred

NO homologous recombination

Question 23

Hfr x F- conjugation

Answer 23

Bacterial genes transferred from Hfr to F-
Process begins at OriT, tra operon is the last thing transferred

Homologous recombination

Question 24

Generalized transduction

Answer 24

A lytic bacteriophage incorporates bacterial chromosome into its phage head
When the phage infects another bacteria, DNA can be incorporated via homologous recombination

Question 25

Specialized transduction

Answer 25

``` Lysogenic phage incorporates into the chromosome as a prophage Some event (UV damage) leads to conversion to a lytic lifecycle ``` Small portion of the chromosome is packaged into phage head after excision from the genome (only genes adjacent to phage insertion are transferred)

Question 26

Three general categories of antibiotic resistance

Answer 26

Intrinsic Chromosome-mediated Plasmid-mediated

Question 27

Intrinsic antibiotic resistance

Answer 27

Unable to be horizontally transferred Not increasing among bacterial populations i.e. lack of an antibiotic target (lack of peptidoglycan)

Question 28

Chromosome-mediated antibiotic resistance

Answer 28

Genes encode antibiotic resistance Arises via random mutation or horizontal gene transfer i.e. penicillin-binding proteins, DNA gyrase, etc.

Question 29

Plasmid-mediated antibiotic resistance

Answer 29

Genes on plasmid encode antibiotic resistance | Usually degrade or modify antibiotic, or pump it out of cell

Question 30

Resistance factor

Answer 30

Has a resistance transfer factor and a resistance determinant

Question 31

Resistance transfer factor

Answer 31

Equivalent to F-factor because it encodes everything needed for conjugation

Question 32

Resistance determinant

Answer 32

Gene(s) for drug resistance

Question 33

Transposons

Answer 33

Mobile DNA elements that can move from one molecule of DNA to another Palindromic sequences

Question 34

TnpA

Answer 34

Enzyme (transposase) required for transposon movement

Question 35

Integrons

Answer 35

Can capture antibiotic resistance cassettes and integrate them into the bacterial DNA Often associated with large mobile genetic elements, like transposons

Question 36

Pathogenicity islands

Answer 36

Region of bacterial chromosome acquired through horizontal gene transfer Often carry coordinately regulated virulence genes surrounded by insertion sequences