Prokaryotic genomes and cell division

Question 1

Three characterisations of a plasmid

Answer 1

circular
small in comparison to prokaryotic chromosomes
replicate independently

Question 2

R plasmids

Answer 2

typically confer antibiotic resistance

Question 3

Plasmid incompatibility group

Answer 3

two plasmids from the same incompatibility group are incompatible with each other and they interfere with each others replication

Question 4

tra genes

Answer 4

make a plasmid self transmissible

Question 5

Where does chromosomal replication begin?

Answer 5

oriC (origin of replication)

Question 6

hemimethylated DNA

Answer 6

only old strand is methylated

Question 7

How are new DNA strands told apart from old DNA strand

Answer 7

absence of methyl groups

Question 8

SeqA

Answer 8

binds to hemimethylated DNA and prevents DNAa from binding

Question 9

What DNA can SesA bidn do

Answer 9

mature DNA

Question 10

HDAa

Answer 10

ATPase that hydrolyses DNAa-ATP to DNAa-ADP

Question 11

multiple replication forks

Answer 11

allow G to be 20 mins despite whole genome replication taking 40 mins

Question 12

Where does replication of ColE1 plasmids occur?

Answer 12

at poles of cell, away from nucleoid

Question 13

Fts proteins

Answer 13

important proteins involved in prokaryotic cell division

Question 14

FtsZ

Answer 14

Tubulin homologue that self assembles to form a membrane-associated ring structure which is the cell division plane

Question 15

Divisome

Answer 15

large protein complex in bacteria that mediates cell division

Question 16

Zip A

Answer 16

anchor that connects and stabilises FtsZ ring to the cytoplasmic membrane

Question 17

FtsA

Answer 17

recruits FtsZ and other divisome proteins

Helps FTsZ ring connect to cytoplasmic membrane

Question 18

FtsI

Answer 18

facilitates synthesis of peptidoglycan in the division septum

Question 19

FtsK

Answer 19

assists in chromosome separation

Question 20

MinC

Answer 20

x

Question 21

MinE

Answer 21

oscillates between cell poles, sweeping MinC and MinD aside as it does so causing the centre of the cell to have the lowest concentration of these proteins

Question 22

Min System

Answer 22

System of proteins that prevent septation and polymersiation of FtsZ at poles; ensures division occurs mid cell.

Question 23

Nucleoid occlusion

Answer 23

Defence mechanism that prevents chromosomes from being bisected by septum formation

Question 24

MreB

Answer 24

protein in most rod shaped bacteria that forms bands perpendicular to the cell wall and directs peptidoglycan synthesis

Question 25

Crescentin

Answer 25

Protein in Caulobacter which causes cell shape to curve by localising at the concave surface of the cell and associating helices of the crescentin filaments with the cytoplasmic side of the cell membrane

Question 26

alphaproteobacteria

Answer 26

Lack MreB but still have polar growth
Polar growth or budding rather than intercalated growth (growth all the way round the cell wall rather than from one end specifically)

Question 27

Bacteria with ? depend on Mreb

Answer 27

Lateral dispersed synthesis at multiple points on the cell wall
(lateral elongation)

Question 28

MreB associated with what shape bacteria

Answer 28

rod shaped

Question 29

Lack of MreB associated with what shape bacteria

Answer 29

coccoid

Question 30

Bactoprenol

Answer 30

C55 alcohol that flips peptidoglycan monomer across hydrophobic cell layer

Question 31

How does bactoprenal insert peptidoglycan monomers into the existing chain? (3)

Answer 31

1. autolysins hydrolyse the glycosidic backbone of peptidoglycan
2. Transglycosylases stitch in the new unit
3. Transpeptidases link DAP to D-Ala to form cross link in transpeptidation reaction

Question 32

Penecillin bacterial cell division target

Answer 32

transpeptidation

Question 33

Actinomycin

Answer 33

antibiotic that inhibits transcription by attacking RNA polymerase

Question 34

Streptomycin

Answer 34

antibiotic that inhibits translation

Question 35

Beta lactamases

Answer 35

bacterial resistance proteins that break down penecillin