L11, 12 - Genetics of Bacteria

Question 1

Nutrient Broth contains

Answer 1

rich media derived from yeast extract and casein

Question 2

Minimal media contains

Answer 2

Na+, K+, Mg2+, Ca2+, Fe2+, NH4+, Cl-, phosphate buffer ph7, glucose as carbon source

Question 3

What is Prototroph?

Answer 3

a bacteria which can grow on minimal media and synthesis all necessary amino acids, vitamins and lipids

Question 4

What is Auxotroph?

Answer 4

When a bacteria will grow only if an extra ingredient is added to minimal media e.g. an amino acid

Question 5

Lag phase

Answer 5

initial period where bacteria adapt to media

Question 6

Exponential or Log phase

Answer 6

period of rapid growth where the bacteria are dividing in a fixed time interval called the doubling time

Question 7

Stationary phase

Answer 7

Cells stop dividing due to limited nutrients

Question 8

Escherichia coli

Answer 8

has a circular double stranded DNA genome which is 4,600 kilo bases pairs (kb)

Question 9

What are the 3 methods of genetic exchange in bacteria vis horizontal gene transfer?

Answer 9

Conjugation, transduction and Transformation

Question 10

What is Conjugation?

Answer 10

• Transfer of plasmid

- Transfer of the bacterial genome when a plasmid capable of conjugation is integrated into the bacterial genome

Question 11

What is Transduction?

Answer 11

• bacteriophage can package a DNA fragment from the bacterial genome and transfer it to another bacterial cell

Question 12

What is Transformation?

Answer 12

• uptake of DNA fragments by the bacteria from the environment

Question 13

To enhance the level of competency in a population of E.coli cells, they can be grown in…

Answer 13

rich liquid culture, harvested in the exponential growth phase and treated with a SALT SOLUTION

Question 14

Linear pieces of DNA need to integrate into the E.coli genome by …

Answer 14

Recombination in order to survive

Question 15

What happen to the linear pieces of DNA that did not integrate with the E.coli genome?

Answer 15

They cannot survive and will be digested by DNase activity to single nucleotides

Question 16

What does a bacteriophage composed of?

Answer 16

An icosahedral head, hollow protein sheath and sometimes a set of tail fibres

Question 17

Types of bacteriophage

Answer 17

T4 phage and Lamda phage

Question 18

What are the 2 types of Transduction by bacteriophage?

Answer 18

Generalised transduction and specialised transduction

Question 19

What is generalised transduction?

Answer 19

it is the transfer of any bacterial genes, is carried out by bacteriophages that cannot distinguish between phage and bacterial DNA when assembling virus particles

Question 20

What is specialised transduction?

Answer 20

it is carried out only by temperate phages whose genome integrates into the bacterial genome and the inly genes transferred are those close to the integration site

Question 21

Size of F plasmid

Answer 21

100 kb

Question 22

The feature of F plasmid

Answer 22

1) approximately 30 transfer (tra) genes
2) an origin of replication (oriV)
3) an origin of transfer (oriT)
4) Three insertion sequences (IS)

Question 23

Features of R plasmids

Answer 23

1) have tra genes so can conjugate between different species of bacteria
2) carry genes that confer multiple antibiotic resistance
3) large 100kb

Question 24

Features of ColEl plasmids

Answer 24

1) small (6.6 kb) and does not carry tra gene cluster so CANNOT move by itself between different bacteria
2) carries ColEl gene that produces a protein colicin which is excreted from the cell and toxic to other bacteria (not the host)

Question 25

Features of Ti plasmids

Answer 25

1) Large (200 kb) have tra genes so can conjugate between different species of bacteria
2) also able to transfer the T-region of plasmid into plant cells
3) Integration of T-region into plant chromosomes cause crown gall disease

Question 26

Hfr strains

Answer 26

when F plasmid integrate into the bacteria genome