bacterial genetics

Question 1

how many genes does e. coli k-12 have?
ans: 4,..

Answer 1

4, 288

Question 2

how long does e. coli k-12 replication take?
ans: 8…

Answer 2

84.3 minutes

Question 3

what 4 things can plasmids provide to bacteria?

Answer 3

• resistance
• metabolic function
• virulence
• the ability of conjugation

Question 4

define mutagens

Answer 4

agents that increase mutation rate

Question 5

how do acridine dyes act as mutagens?

Answer 5

• by introducing frameshift mutations
• and insert themselves between DNA bases, which create kinks
• both of which result in additions or deletions

Question 6

define silent mutations

Answer 6

• a single base change that causes no change to the amino acid sequence
• due to the degeneracy of the genetic code

Question 7

define missense mutations

Answer 7

• a base change that results in the substitution of an amino acid in the sequence
• results in less-functional proteins

Question 8

define nonsense mutations

Answer 8

• a base change that responds in the introduction of a stop codon
• results in an incomplete and non-functional protein

Question 9

which enzyme supercoils bacterial dna?

Answer 9

endonuclease

Question 10

what enzyme undoes the supercoiling of bacterial dna?

Answer 10

topoisomerases

Question 11

how many base pairs is the mycoplasma genome?
ans: 5..

Answer 11

580 Kbp; relies on other organisms for survival

Question 12

what kind of replication is bacterial replication?

Answer 12

semiconservative

Question 13

where does replication start in bacteria?

Answer 13

at the oriC

Question 14

how many arrest sites are at the terminator region of bacteria?

Answer 14

at least 8

Question 15

describe salmonella enterica

Answer 15

• causes gastroenteritis
• related to e. coli
• contains lots of conserved bacterial genes

Question 16

define the operon

Answer 16

a group of genes controlled by one promoter

Question 17

describe the 4 parts of the operon
(ans: r, p, o, s)

Answer 17

• regulatory gene
• promoter
• operator
• structural genes

Question 18

what is the function of the regulatory gene?

Answer 18

encodes a regulatory protein which binds to the operator to stop transcription

Question 19

what is the function of the promoter?

Answer 19

where the RNA polymerase binding site

Question 20

describe the function of the structural genes

Answer 20

these are the proteins that the operon controls

Question 21

name an example of an inducible operon

Answer 21

the lac operon, uses activator proteins

Question 22

name an example of repressor operon

Answer 22

trp - tryptophan

Question 23

what laboratory techniques are used for transformation?

Answer 23

electroporation, calcium washing

Question 24

what triggers transformation in bacteria?

Answer 24

nutrient depletion, stressful conditions

Question 25

what is the competency?

Answer 25

the ability of bacteria to take up extragenous dna

Question 26

what two types of protein are involved in the uptake of DNA?

Answer 26

- dna binding proteins uptake dna from the surroundings - dna translocase recruits one strand of dna

Question 27

what protein is involved in the stabilisation of ssDNA?

Answer 27

RecA

Question 28

how is generalised transduction used in the lab?

Answer 28

to move plasmids between bacteria

Question 29

describe the process of transduction

Answer 29

- phage infects bacterium - bacterial dna cleaved - phage dna replicated - some capsules assemble with bacterial dna by mistake - phage injects bacterial dna into new bacterium - bacterial dna joins new genome due to homologous pairing

Question 30

what are f+ cells?

Answer 30

bacterial cells that contain the f plasmid, allowing them to conjugate with other cells

Question 31

what is the tra region?

Answer 31

the area of the f plasmid that contains the genes for conjugative transfer

Question 32

what are insertion sequences?

Answer 32

areas of the f plasmid that contain homology to allow integration into the bacterial genome

Question 33

how does the oriT relate to the tra region on the f plasmid spatially?

Answer 33

oriT is at the beginning of replication, the tra region is at the end

Question 34

define Hfr cells

Answer 34

high frequency of recombination; cells which have the f plasmid integrated into the genome

Question 35

describe the mechanism of conjugation

Answer 35

- pilus attaches to f- bacterium - bacteria are brought closer together and envelopes fuse - one strand of dna is transferred to the F- cell - both cells synthesise a complementary strand - creating two F+ bacteria

Question 36

why are Hfr cells unsuccessful at transferring the tra region?

Answer 36

DNA is labile, so the strand often breaks before the tra region can be transferred - the F- receives some of the f plasmid, but cannot perform conjugation