The Mess That Is Micro - V - Genetics

Question 1

Transformation

Answer 1

Ability to take up naked DNA (i.e. from cell lysis) from the environment (competence).

ESPECIALLY SHIN bacteria!

Any DNA can be used.

Adding deoxyribonuclease to environment will degrade naked DNA in medium - no transformation will be seen.

Question 2

F+ x F-

Answer 2

F+ plasmid contains genes required for sex pilus and conjugation. Plasmid (dsDNA) is replicated and transferred through pilus from F+ cell. No transfer of chromosomal gene.

Question 3

F+

Answer 3

F+ plasmid contains genes required for sex pilus and conjugation.

Question 4

Hfr x F-

Answer 4

F+ plasmid can become incorporated into bacterial chromosomal DNA, termed high frequency recombination (Hfr) cell. REplication of incorporated plasmid DNA may include some flanking chromosomal DNA. Transfer of plasmid and chromosomal genes.

Question 5

Transposition

Answer 5

Segment of DNA (i.e. transposon) that can jump (excision and reintegration) from one location to another, can transfer genes from plasmid to chromosome and vice versa. When excision occurs, you may include some flanking chromosomal DNA, which can be incorporated into a plasmid and transferred to another bacterium. Example: antibiotic resistance genes on R plasmid.

Question 6

Generalized transduction

Answer 6

A packaging event in which lytic phage infects bacterium, leading to bacterial DNA cleavage. Parts of bacterial chromosomal DNA may become packaged in viral capsid. Phage infects another bacterium, transferring these genes.

Question 7

Specialized transduction

Answer 7

An excision event. Lysogenic phage infects bacterium; viral DNA incorporates into bacterial chromosome. When phage DNA is excised, flanking bacterial genes may be excised with it. DNA is packaged into phage viral capsid and can infect another bacterium.

Question 8

What bacterial toxins are encoded in a lysogenic phage?

Answer 8

ABCDE
ShigA-like toxin
Botulinum toxins
Cholera toxin
Diptheria toxin
Erythrogenic toxin of Strep pyogenes

Question 9

Recombination

Answer 9

Exchange of genes between 2 chromosomes by crossing over within regions of significant base sequence homology.

Question 10

Reassortment

Answer 10

When viruses with segmented genomes (eg influenza virus) exchange segments. High frequency recombination. Cause of worldwide influenza pandemics.

Question 11

Complementation

Answer 11

When 1 of 2 viruses that infect the cell has a mutation that results in a nonfunctional protein. The nonmutated virus complements the mutated one by making a functional protein that serves both viruses.

Question 12

Phenotypic mixing

Answer 12

Occurs with simultaneous infection of a cell with 2 viruses. Genome of virus A can be partially or completely coated (forming pseudovirion) with the surface proteins of virus B. Type B protein coat determines the tropism (infectivity) of the hybrid virus. However the progeny from this infection have a type A coat that is encoded by its type A genetic material.