Bacterial Genetics

Question 1

How do prokaryotes achieve genetic change?

Answer 1

~ conjugation (plasmids)
~ transduction (uptake of ‘take’ DNA)
~ transformation (utilises bacteriophages)

Question 2

Bacterial genomes

Answer 2

~ one essential circular dsDNA chromosome

~ may contain additional, extrachromosomal, small, circular plasmids

Question 3

Name the three types of different plasmids.

Answer 3

sex
R
col

Question 4

Sex plasmids

Answer 4

e.g. F (fertility) plasmid - large, stringent replication, self mobile, episome
~ mediate transfer of bacterial genes by CONJUGATION

Question 5

Episome

Answer 5

may exist as free circular plasmid or may be integrated into chromosome

Question 6

R plasmids

Answer 6

R = resistance factors
~ large, self mobile
~ encodes resistance to antibiotics, toxins, heavy metals

Question 7

Col Plasmids

Answer 7

~ small, relaxed replication
~ encodes biological factors
~ does not encode for plasmid transfer - needs R/F plasmids for transfer
~ manipulated for human cloning

Question 8

Who discovered F plasmid-mediated conjugation?

Answer 8

Lederberg and Tatum (1946)

Question 9

tra genes

Answer 9

transfer genes

Question 10

OriT

Answer 10

Origin of transfer

Question 11

Hfr strain

Answer 11

High frequency transfer strain

~ discovered by Hayes and Cavalli-Sforza

Question 12

Cotransformation frequency

Answer 12

can be used as a measure of link and used to map bacterial gene order

Question 13

Generalised transduction

Answer 13

mediated by virulent bacteriophages e.g. P1vir

Question 14

Specialised transduction

Answer 14

mediated by temperate bacteriophages e.g. lander have both lytic and lysogenic life-cycles