Horizontal gene transfer

Question 1

What is horizontal gene transfer (HGT)?

Answer 1

HGT is how bacterial cells transfer genetic information between each other in the same generation

Question 2

How is horizontal gene transfer different from vertical gene transfer?

Answer 2

Vertical gene transfer indicated genes being transferred throughout generations – e.g. a bacterial mother cell transfers its DNA to its daughter cells, while horizontal gene transfer indicates genes being transferred in the same generation

Question 3

What are the three methods of HGT?

Answer 3

Transduction, transformation and conjugation

Question 4

Which two mobile genetic elements enable conjugation?

Answer 4

Transpodons (“jumping genes”) and plasmids

Question 5

Summarize the process of conjugation

Answer 5

Bacteria make cell-to-cell contact via a conjugation pilus, forming a “bridge” between cells. Nuclease “knicks” one of two DNA strands in the plasmid of the “original cell”, allowing it to transfer the genetic information to the other cell. Once the plasmid is inside the other cell it produces a copy, transforming it back into DNA. The “second” cell now has the same set of DNA as the original cells plasmid. The second cell now also has the ability to form a conjugation pilus.

Question 6

Summarize the process of transformation

Answer 6

“Competent” bacteria integrate new, free floating DNA into their genome. This new DNA is often from lysed bacteria. The new DNA and the bacterias original DNA are rearranged into a new “hybrid” genome. This can lead to phenotypic changes

Question 7

Summarize the process of transduction

Answer 7

Bacteriophages accidentally transfer bacterial DNA between bacteria.

Question 8

What does competency mean in the context of transformation in HGT?

Answer 8

Competency indicates how permeable the cell wall of a bacteria is. The more permeable the higher competency

Question 9

What is generalized transduction?

Answer 9

Transduction where the DNA transferred by the bacteriophages is randomly picked up

Question 10

What is specialized transduction?

Answer 10

Transduction where the DNAtransferred by bacteriophages is picked up near the insertion site.

Question 11

What is the benefit of horizontal gene transfer?

Answer 11

Higher bacterial adaptability and increased bacterial diversity