Bacterial Genetics

Question 1

plasmids

Answer 1

double-stranded, often circular DNA sequences that are capable of autonomously replicating in a host cell
*NOT part of the core chromosome

Question 2

genomic thrift

Answer 2

majority of bacterial genome is coding for something (selects for rapid growth, ditching genes that slow them down/are not super important)

Question 3

unique functions that a plasmid may provide a host bacteria

Answer 3

-antibiotic resistance
-toxin production
-novel biochemical functions or surface molecules

Question 4

copy and paste (retro) transposons in bacteria

Answer 4

replicative

Question 5

cut and paste transposons in bacteria

Answer 5

conservative (no additional copies)

Question 6

operons

Answer 6

*bacterial genes organized in clusters of related genes
*genes in an operon turn on or off TOGETHER
*a single promoter regulates all of the genes in an operon
*allow efficient use of resources and genomic space (only express the genes when needed)

Question 7

operon for vancomycin resistance

Answer 7

when vancomycin is sensed, the cell switches to making an alternative cross-linker to function in presence of antibiotic
*switches back to off when no vancomycin present

Question 8

how do bacteria divide / replicate

Answer 8

binary fission

Question 9

wild-type bacteria

Answer 9

description of a bacterium that is found MOST ABUNDANTLY in nature

Question 10

mutant bacteria

Answer 10

bacterium that differs genetically from the wild-type; the mutant has a genotype different from the wild-type strain, which may or may not result in a readily observable trait

Question 11

2 primary mechanisms for generating genetic diversity in bactera

Answer 11

1. vertical transmission - spontaneous and random mutations and selection for bacteria with enhanced properties (slow)
2. horizontal transmission - gene transfer from other microorganisms (rapid)

Question 12

4 mechanisms of horizontal gene transfer

Answer 12

1. transformation
2. transduction
3. conjugation
4. transposition

Question 13

horizontal gene transfer: transformation

Answer 13

*uptake by a bacteria of naked DNA
*find DNA in the environment and put it into its own chromosome
*can occur between unrelated bacteria and between domains

Question 14

examples of transformation in real life

Answer 14

*strep. pneumoniae
*haemophilus influenza
*can acquire capsule protein (virulence factor)

Question 15

horizontal gene transfer: transduction

Answer 15

*infection of non-lethal virus carrying bacterial genes
*acquisition of genes from a BACTERIOPHAGE (injection of DNA)

Question 16

lytic phages

Answer 16

phages that cause KILLING of host bacterium

Question 17

lysogenic phage

Answer 17

phage that can survive in the bacterium without killing; usually integrated into the bacterial chromosome

Question 18

temperate phage

Answer 18

phage capable of undergoing BOTH lytic or lysogenic development

Question 19

virulent phage

Answer 19

phage capable of undergoing ONLY lytic development

Question 20

lysogen

Answer 20

bacterium harboring a lysogenic phage

Question 21

examples of transduction

Answer 21

*many bacterial exotoxins coded for by phages
1. group A strep
2. clostridium Botulinum
3. vibrio Cholerae
4. Corynebacterium diphtheriae
5. Staph aureus
6. E. coli (shiga toxin)

Question 22

restriction systems that limit transduction

Answer 22

1. methylating enzyme protects DNA
2. endonuclease cuts unmethylated DNA

Question 23

horizontal gene transfer: conjugation

Answer 23

*plasmid-mediated exchange of information between bacteria in contact
*can NOT go between gram + and gram -
*not all plasmids are conjugative

Question 24

horizontal gene transfer: transposition

Answer 24

*exchange of genetic information via mobile genetic elements
*can be cut and paste or copy and paste
*inverted repeats at either end of the transposons

Question 25

mecA and MRSA

Answer 25

*mecA is carried on a mobile genomic element (transposon)
*encodes an ALTERED PENICILLIN BINDING PROTEIN
*causes resistance to beta-lactam antibiotics

Question 26

drug-resistance of Neisseria gonnorhea

Answer 26

swaps out the pilin genes to hide from our immune system