Microbial Genetics

Question 1

1. The student will be able to define the bacterial genome

Answer 1

Totality of its genetic material: The chromosome (long circular dsDNA), Extrachromosomal genetic elements (Plasmids)

Question 2

2. The student will be able to explain the major steps of prokaryotic DNA replication

Answer 2

Initiated at specific sequence in chromosome called Ori.
Binding of initiator protein, synthesis of RNA primers, unwinding of DNa by helicase, 2 replication forks.

Initiation, Elongation, Termination

Question 3

3. The student will be able to define a bacteriophage

Answer 3

Virus that replicates inside a bacteria. Classified as virulent / temperate.

Question 4

4. The student will be able to explain the major differences between virulent and temperate phages

Answer 4

Virulent: results in death by cell lysis (lytic cycle)
Temperate: lysogenic cycle

Question 5

The student will be able to explain the differences between conjugation, transduction,and transformation

Answer 5

Conjugation: transfer genes via contact by F pilus. F+ has F plasmid, gives to F- cell which becomes F+.
Transduction: Transfer genes via phage vector. No cell-cell contact
Generalized transduction: phage DNA completely replaced by bacterial DNA
Specialized transduction: DNA consists of both phage DNA and bacterial DNA
Transformation: Transfer of genes from one cell by means of naked DNA. Example: cell lysis frees dna fragments, taken up by recipient cell.

Question 6

6. The student will be able to describe Griffith’s transformation of pneumococcus

Answer 6

S. Pneumoniae cells have capsules, produce Smooth (S) mucoid colonies (lethal)
Mutants without capsules = rough (R) colonies
Mouse with R strain = lives. Mouse with S strain = dies. Mouse with heat-killed S strain = lives. Mouse with R strain + Heat killed S strain = dies.
Basically the killed S bacteria mixed with living R bacteria to live.