Charter 6 and 10 Lec. 3

Question 1

Lateral gene transfer

Answer 1

The transfer of genetic material from one organism to another that is not an offspring.

Question 2

Genetic Recombination

Answer 2

The physical exchange of DNA between genetic elements.

Selective medium can be used to detect rare genetic recombinants.

Question 3

Three kinds of lateral gene transfer

Answer 3

Transformation
Transduction
Conjugation

Question 4

Transformation

Answer 4

Uptake of naked DNA.
Discovered by Frederick Griffith in the late 1920’s.
This process set the stage for the discovery of DNA.

Question 5

Griffith’s experiment

Answer 5

Rough strain –> mouse lives.
Smooth strain–> mouse dies.
heat killed smooth strain–> mouse lives.
rough strain and heat killed smooth strain–> mouse dies.

Question 6

Transformation: Competent

Answer 6

Cells capable of taking up DNA and being transformed.

• competence is highly regulated.
• procedures are necessary to make cells competent.
• electricity can be used to make cells uptake DNA.

Question 7

Transformation: Factors promoting transformations

Answer 7

1. uptake mechanism and rate
2. quantity of environmental DNA
3. longevity of environmental DNA
4. usefulness and incomparability of DNA
5. Various inhibitors

Question 8

Transduction

Answer 8

Gene transfer by viruses.
Two modes:
-generalized transduction
-specialized transduction: DNA from a specific region integrated directly into virus genome.

Question 9

Generalized transduction

Answer 9

DNA derived from virtually any portion of host genome packaged inside mature virion.

• virus can be temperate or virulent
• low efficiency

Question 10

specialized transduction

Answer 10

DNA from specific region of host chromosome integrated directly in virus genome.

• transducing efficiency can be high
• DNA of temperate virus excises incorrectly and takes adjacent host genes

Question 11

Conjugation: bacterial conjugation

Answer 11

Mechanism of genetic transfer that involves cell to cell contact.

• plasmid encoded mechanism
• donor cell: conjugative plasmid
• recipient cell: no plasmid

Question 12

Conjugation: F plasmid

Answer 12

Circular DNA molecule.
Contains genes that regulate DNA replication.
Transposable elements.
Contains TRA genes that encode transfer functions.

Question 13

Conjugation: sex pilus

Answer 13

Essential for conjugation.

-only produced by donor cell.

Question 14

Conjugation: DNA synthesis

Answer 14

Necessary for DNA transfer by conjugation.

-rolling circle replication

Question 15

Hfr strains and chromosome mobilization

Answer 15

F plasmid is an episome, can integrate into host chromosome.
Cells possessing nonintegrated F plasmid F+.
Cells possessing Hfr

Question 16

Hfr strains and chromosome mobilization: presence of F plasmid

Answer 16

Results in alternations of cell properties.

Question 17

Hfr strains and chromosome mobilization: insertion sequences

Answer 17

Present in both F plasmid and E. coli chromosome.

Plasmid is now part of chromosome.

Question 18

Hfr strains and chromosome mobilization: does not become Hfr (4)

Answer 18

• Only a portion of the integrated F plasmid is transferred by the donor.
• Hfr strains that differ in integration position of F plasmid in chromosome transfer genes in different order.
• Genetic crosses with Hfr strains can be used to map order of genes on chromosome.
• Identification of recombinant strains requires conditions recombinants can grow but parents can not.

Question 19

Hfr strains and chromosome mobilization: F plasmid

Answer 19

Previously integrated F plasmids that have excised and captured some chromosomal genes.

Question 20

Complementation

Answer 20

Merodiploid: bacterial strain that carries two copies of any particular chromosomal segment.

Complementation: process by which a functional copy of a gene compensates for a defective copy.

Question 21

Complementation Tests

Answer 21

Determines if 2 mutations in same or different genes.

• different (trans)
• same (cis)

Question 22

Gene transfer in archaea

Answer 22

Archaea contain single circular chromosome.

Genetic manipulation of archaea lags behind bacteria.

Question 23

Gene transfer in archaea: Examples

Answer 23

Transformation, transduction, and conjugation.
Works well in archaea.
-especially halophiles.