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Flashcards in Lab: Genetic Exchange Deck (14):
0

Three mechanisms of genetic exchange amongst bacteria

- transformation
- transduction
- conjugation

1

Conjugation

Allows genetic exchange to occur between two bacterial cells in direct contact with one another and form a sex pilus

2

Plasmid

Circular pieces of dsDNA that exist and replicate independently of chromosomal DNA

Transferred from F+ donor to F- recipient

Contains F factor ( allows plamsmid to be integrated)

3

Bacterial transformation

Microorganism takes up naked DNA from it's environment

4

Organisms that undergo transformation are considered

Competent

5

Natural transformation

Organisms have membrane-bound proteins that actively transport DNA into the cell

6

Artificial transformation

- electroporation: electric current applied and causes pored to be generated in cellular membrane allowing DNA to enter cell

- heat-shock in calcium chloride: causes membrane to become permeable to DNA

7

Selecting for transformed bacteria

Use marker proteins that give a selective advantage to the orgs with transformed gene and allows it to be distinguished

8

Transduction

Viral phage or bacteriophage infects and transfers genetic material to a bacterial cell.

9

Components of viral phage

- head (containing genetic material - DNA, RNA, both)
- neck extending from head
- collar that sits on top of sheath
- base plate at the end of the sheath
- protein syringe hidden and protected in the sheath above the base plate
- tail fibers extending from the sheath

10

Attachment steps in transduction

- one of the tail fibers attaches to the host cell creating a lock and key connection
- all other fibers then orient themselves to attach to the host cell locking phage onto bacteria
- penetration begins
- once fibers attached, conformational change, base plate pushes sheath up over neck exposing protein syringe that penetrates bacterial cell
- genetic material delivered into cell

11

Vertical gene transfer

passed down through generations

12

Horizontal gene transfer

transferred from an unrelated bacterium
transformation, conjugation, transduction

13

F factor

- segment of plasmid
- when expressed sex pilus forms
- contains gene that allows for chromosomal integration
must be present for conjugation to occur