Lecture 10

Question 1

What is used as a carbon source in minimal media?

Answer 1

Glucose

Question 2

Are bacteria haploid or diploid?

Answer 2

Haploid and so only contain one copy of each gene

Question 3

If a symbol in bacterial genetics has a minus sign (eg: bio-), what does this mean?

Answer 3

The bacteria requires the substance added as a supplement to minimal medium (eg: bio- means requires biotin)

Question 4

If a symbol in bacterial genetics has an ‘r’ sign (eg: str(r)), what does this mean?

Answer 4

Resistant to the antibiotic or substance

Question 5

If a symbol in bacterial genetics has an ‘s’ sign (eg: str(s)), what does this mean?

Answer 5

Sensitive to the substance or antibiotic

Question 6

What is transformation?

Answer 6

Uptake of DNA fragments by the bacteria from the environment

Question 7

How is plasmid pGLO transformed into competent E.coli cells?

Answer 7

Harvest cells in ‘exponential growth’ phase
Plasmid pGLO containing ampicillin resistance gene is added to tube with E.coli
Plasmid will stick to the surface of the cell, plasmid induced to move into ‘heat-shock’ by putting it at 42 degrees
Cells placed on LBE media with ampicillin
Only E.coli cells taken up by pGLO can form colonies as they have the resistance gene
Plates incubated at 37 degrees for a day then placed at 4 degrees for viewing

Question 8

What is transduction?

Answer 8

Bacteriophage can package a DNA fragment from the bacterial genome and transfer it into another bacterial cell through the lytic cycle

Question 9

How does conjugation occur?

Answer 9

F+ cell (bacteria that contains F plasmid) forms a conjugation pillus which grows and attaches to an F- cell (bacteria that doesn’t have F plasmid)
Protein complex called the relaxosome binds to the origin transfer at the F+ and cleaves one strand then binds to the end of that strand
Relaxosome moves to the conjugation pillus and interacts with the exporter protein
Single DNA strand is transferred across the conjugation pilus and into the recipient cell
As the strand leaves, DNA replication occurs and produces the same strand

Question 10

What is the Hfr strain?

Answer 10

E.coli cells with a copy of the F plasmid

Question 11

What is an IS element?

Answer 11

Short DNA sequence that can move within a genome

Question 12

How long does transferring the whole F plasmid to another bacteria take?

Answer 12

100 minutes