L36

Question 1

Are bacteria haploid or diploid?

Answer 1

Haploid
X nucleus
X introns

Question 2

What is the structure of the bacterial ribosome?

Answer 2

30S (w/ 16 rRNA)

50S

Question 3

What are the 3 major bacterial genetic elements?

Answer 3

1. Chromosome
2. Plasmid = independently replicating
3. Transposon = integrates into plasmid or chromosome to replicate

Question 4

What is the structure of transposons?

Answer 4

Start & end with inverted repeats
- allow for base pairing with the DNA it will integrate in with
tnpA = transposase gene
Ab resistant genes

Question 5

What are insertion sequences?

Answer 5

Transposon - recongizable genetic patterns (i.e. no Ab resistance)

Question 6

What is the action of transposons/insertion sequences?

Answer 6

Can inactivate target genes & cause genetic rearrangements

Question 7

What is a bacteriophage?

Answer 7

Virus that infects bacteria
Can lyse & kill cells (lytic)
OR
Incorporate into bacterial DNA, replicate, then lyse cell (lysogenic)

Question 8

What are pathogenicity islands?

Answer 8

DNA w/ virulence genes
@ “house keeping” part of the DNA
Nonpathogenic strains of bacteria can acquire PIs & gain properties responsible for disease

Question 9

What are the 3 mechanisms of genetic exchange?

Answer 9

Transformation
Conjugation
Transduction

Question 10

What is transformation?

Answer 10

Naked DNA from 1 cell taken up by another cell w/o participation of other bacteria/virus

Question 11

What is conjugation?

Answer 11

Genetic transfer via cell-cell contact

Sexual mating

Question 12

How does E.Coli accomplish conjugation?

Answer 12

F factor = fertility factor
- Encodes the sex pilus
Is an episome = capable of integrating into chromosome

Question 13

What is high frequency recombination?

Answer 13

Once F factor is in the chromosome, can lead adjacent chromosomal regions out of donor cell and into recipient via single stand & replication

Question 14

What is transduction?

Answer 14

Transfer of DNA between bacteria via VIRUSES

Question 15

What are the 2 types of transduction?

Answer 15

Specialized = phage always integrates into specific site in host chromosome
Generalized = gene transfer in random manner

Question 16

What is a regulon?

Answer 16

Multiple DNA operons linked together in a global regulatory network
Doesn’t have to be a physical link

Question 17

Where is the most important site of bacterial regulation of DNA replication?

Answer 17

Initiation of transcription

Question 18

What is a 2 component regulatory system?

Answer 18

Sensory = sees changes in environment, transmits signal to regulator 
Regulator = binds DNA and changes transcription via phosphorylation

Question 19

What is quorum sensing?

Answer 19

How bacteria secrete low molecular weight compounds to signal other bacteria to turn on specific gene expression
Low [ ]s - no effect b/c diluted
High [ ]s - regulation of genetics in other bacterial

Question 20

How does an autoinducer work?

Answer 20

Binds & actviates transcriptional regulator to turn on specific genes
Due to quorum sensing

Question 21

What are simple ways that a bacteria can change the way its DNA is arranged to alter pathogen properties?

Answer 21

Duplication
Gene amplification
Deletion

Question 22

What is phase variation?

Answer 22

Reversible switch on/off of expression phases to change a pathogen’s properties
Genetic mechanism that can lead to antigenic variation

Question 23

What is antigenic variation?

Answer 23

Expression of antigenically distinct but functionally conserved moieties within a population
To change a pathogen’s properties
“Gene conversion”

Question 24

Give an example/explain phase variation by gene inversion.

Answer 24

Salmonella
@ transcription
Alternate between H1 & H2 antigens
Controlled by recombinase that acts on inverted repeats to change orientation of genetic fragment

Question 25

Give an example/explain slipped strand mispairng.

Answer 25

@ translation
Delete 1+ base pairs –> frame shits & premature stop codons
Reversible so silent genes can be expressed

Question 26

What is an integron?

Answer 26

Incorporates promotor-less genes and converts them to functional genes