Lectures 13-15 - Bacterial And Viral Genetics

Question 1

What makes bacteria valuable research objects?

Answer 1

Small size, rapid repro, selective media, simple structures, genetic variability

Question 2

What do bacteriophages do on solid media?

Answer 2

Produce clearings, plaques on plate

Question 3

Lytic cycle

Answer 3

Phage binds to bacteria
Phage dna enters host cell
Host dna is digested
Phage dna replicates
Host cell transcribes phage proteins
Cell lyses and phage can infect new cells

Question 4

Lysogenic cycle

Answer 4

Phage binds to bacteria
Phage dna enters host cell
Phage dna integrates into bacterial chromosome
Bacteria replicates with phage dna in it
Phage dna may separate from host dna and go into lytic cycle

Question 5

What are plasmids?

Answer 5

Small circular dna, where Additional genetic material resides, an replicate independently of chromosome

Question 6

Phenotypes of bacteria

Answer 6

Colony colour/morphology
Nutritional mutants
Prototrophs and autotrophs
Antibiotic resistance

Question 7

What are the three parasexual processes?

Answer 7

Conjugation
Transformation
Transduction

Question 8

What happens in conjugation?

Answer 8

Cytoplasmic bridge forms between donor cell and recipient cell, dna replicates and transfers to recipient cell via rolling circle replication,

Question 9

What is transformation?

Answer 9

DNA fragments from outside the cell are taken up by recipient cell, crossover leads dna integration

Question 10

What is transduction?

Answer 10

Virus attached to bacterial cell, injects dna, and replicates, taking up bacterial dna in its head instead of viral dna, the cell lyses, and phage carrying bacterial dna inserts that into host cell which takes up bacterial dna instead of viral dna

Question 11

How to distinguish between parasexual processes in bacteria

Answer 11

Cell contact required? - no transformation, yes conjugation, no transduction
Sensitive to dnase? - yes transformation, no conjugation, no transduction

Question 12

What is bacterial competence?

Answer 12

Can bind to exogenous dna and transport it into the cell

Question 13

Conjugation is mediated by?

Answer 13

Fertility factor F factor (episome)

Question 14

What are the three F factor scenarios?

Answer 14

F- cell: no fertility factor
F+ cell: fertility factor
Hfr cell: integrated f factor

Question 15

F+ and F- cross

Answer 15

Conjugation bridge forms, replication of f factor occurs, and recipient cell becomes f+ cell

Question 16

Hfr and F- cross

Answer 16

Conjugation bridge opens and f factor is replicated (plus extra dna from donor Hfr cell), crossing over may occur between donor cell dna and recipient f- cell chromosome, and f factor is not integrated or does not stay in f- cell, end with Hfr and f- cell