Lecture 6 - Replication

Question 1

how to start replication?

Answer 1

replicon - unit of genome in which DNA is replicated. each contains an origin for initiation of replication (OriC)

Question 2

describe dna replication in bacteria

Answer 2

• bubble forms in chromosome
• bidirectionally synthesised

Question 3

function of gyrase

Answer 3

topoisomerase that relieve the strain placed on double helix as it unravels

Question 4

replication termination

Answer 4

• genome contains a lot of termination sites which is recognised by tus protein
• diff sites have one conserved G across all the sequences
• tus protein recognises the C (complementary to G) which binds and inhibits the polymerase and terminates the replication

Question 5

what is a clamp loader

Answer 5

loads beta clamp around DNA. places processivity subunits on DNA at the replication fork

Question 6

what is rolling circle replication

Answer 6

• unidirectional nucleic acid replication that can rapidly synthesize multiple copies of circular molecules of DNA/RNA such as plasmids, phage genomes etc.

Question 7

what are 3 types of gene transfer in prokaryotes

Answer 7

transformation, transduction, conjugation

Question 8

describe the F (fertility) plasmid

Answer 8

• tra genes encoding transfer functions (pilus snthesis and assembly, cell pairing, nicking at oriT) are located in an operon)

Question 9

what kind of strains are formed when F is integrated into bacterial chromosome and how?

Answer 9

Hfr - high frequency of recombination through site specific recombination

Question 10

how is chromosome map determined based on oriT location

Answer 10

genes closest to oriT = higher frequency of being transferred

Question 11

2 types of transduction

Answer 11

generalised = any part of bacterial genome - occurs during lytic
specialised = only specific portions of the bacterial genome carried out by temperate phages that have integrated their DNA into the host chromosome at a specific site in the chromosome