Bacterial Gene Transfer

Question 1

What are the three types of bacterial gene transfer?

Answer 1

Conjugation, Transduction, Transformation

Question 2

What are the characteristics of bacterial gene transfer?

Answer 2

-only part of genome is transferred

Question 3

DNA Recombination

Answer 3

-replacement of one allele with another -enzyme-mediated physical breakage and rejoining of two DNA molecules to form hybrid recombinant molecules

Question 4

What are the types of recombination?

Answer 4

1) homologous 2) site specific 3) transposition

Question 5

Define homologous recombination.

Answer 5

exchange of DNA between homologous donor and recipient DNA strands

Question 6

Transformation

Answer 6

-competence: ability to take up naked DNA (i.e. from cell lysis) from environment

Question 7

Transduction

Answer 7

-mediated by bacteriophage virus -generalized: error in DNA packaging -specialized: aberrant excision of prophage

Question 8

Generalized Transduction

Answer 8

lytic phage infects bacterium, leading to cleavage of bacterial DNA; parts of bacterial DNA become packaged in viral capsid & phage infects another bacterium, transferring the genes

Question 9

Specialized Transduction

Answer 9

lysogenic phage infects bacterium, viral DNA incorporates into bacterial genome; when phage DNA is excised, bacterial genes go with it an get packaged into phage viral capsid –> can go infect another bacterium

Question 10

Conjugation

Answer 10

F plasmid (dsDNA) is replicated and transferred through sex pills from F+ cell to F- cell (no transfer of chromosomal genes)

Question 11

F Plasmid

Answer 11

dsDNA, F pilus genes, transfer (tra) genes, origin (oriT) of transfer, origin (oriV) of replication, IS elements

Question 12

High Frequency Recombination Cell (Hfr)

Answer 12

F plasmid can incorporate into bacterial chromosomal DNA; replication of incorporated plasmid DNA may include some flanking chromosomal DNA; transfer of plasmid and chromosomal genes to F- cell

Question 13

Transposition

Answer 13

segment of DNA that can jump from one location to another (i.e. plasmid to chromosome and vice versa)

Question 14

Insertion Sequences (IS Elements)

Answer 14

-small sequences of DNA that contain direct or inverted terminal repeats -encode transposes that mediates transposition of IS element -no genes unrelated to transposition

Question 15

Transposon

Answer 15

-larger than IS elements -contain direct or inverted terminal repeats, some repeats are IS elements -enode transposase -recognizable phenotype unrelated to transposition