Unit 3 last part of slides

Question 1

How does free plasmid transfer material?

Answer 1

1) F plasmid has oriT
2) TraY/ i binds to OriT and create relaxosome, which is needed to initiate transfer into recipient bacterium
3) TraI nicks DNA at OriT and forms a covalent bond at 5’
4) TraI bound DNA transferred recipient cell via ts44
5) only a single unit is tansferred and single strand gets circularized
6) In donor cell, a complementary strand also needs to be synthesized to replace strand taht was transferred

Question 2

F plasmid integrated conjugation steps

Answer 2

1) Nick of F factor at Orc
2) transfer begins w/ short sequence of F dna and is continuous until contact between two bacteria are broken
3) onceDNA enters recipient cell it is converted to double stranded and may recombine with recipient chormosome

Question 3

Hfr

Answer 3

is bacterium that has an integrated F plasmid w/in its chromosome

chromosomal genes are transferred from Hfr cell to an F- cell more frequently than from an F+ cell

Question 4

What is a copy number?

Answer 4

the number of copies of a plasmid that is maintained in a bacterium (relative to the number of copies of the origin in the bacterial chromosome)

Question 5

Single copy plasmids

Answer 5

exist at one plasmid per bacterial chromosome origin

1 origin replicated only once

Question 6

Multicopy plasmid

Answer 6

exist at more than one copy per bacterial chromosome origin

multiple iniiation events

Question 7

Partition systems ensure that duplicated plasmids are what?

Answer 7

segregated to different daughter cellls produced by division

Question 8

R1 plasmid partitioning steps

Answer 8

ParC on R1 plasmid

1) Par R binds to the ParC site
2) ParR-ParC complex hold daughter plasmid together
3) polymerization of ParM (an actin like ATPase) pushes R1 plasmids apart

Question 9

What is meant by plasmid incompability

Answer 9

Plasmids in a single compatibility group have origins that are regulated by a common control system

hence they cannot coexist in the same bacterial cell b/c they hir origins cannot be distinguisehd

Question 10

ColE1 compatibility system is controlled by?

Answer 10

RNA regulator

Question 11

RNAse H role?

Answer 11

cleaves transcript and generate a primer 3’-OH end

Question 12

Regulator RNA

Answer 12

short antisense that pairs w/transcript and prevents the cleavage that generates the priming end

Question 13

Rom protein

Answer 13

enhances pairing between RNA 1 and the transcript primer

Question 14

RNA priming stage is where regulation occurs via?

Answer 14

1) synthesis of RNA complementary to primer

2) protein encoded by nearby locus

Question 15

RNA I

Answer 15

regulatory RNA is coded by the opposite strand of sequences that encodes for the primer RNA

Pairing of RNA I to primer causes change in structure of primer and creates cleavage

Question 16

Countertranscript

Answer 16

an RNA molecule that prevents an RNA primer from initiation transcription by base pairing w/the primer