11 November: Mechanisms of Genetic Exchange

• High numbers • Single copy of a chromosome • Transcription and translation combined • Short generation time

Conjugation, transformation and transduction

Type of horizontal gene transfer • Plasmid-encoded pilus attaches to another cell + transfers copy of plasmid to another cell

R plasmids (antibiotic resistance), Virulence plasmas (toxins or other disease causing products), and transmissible plasmids (transfer copies of themselves to other cells)

Encodes protein that makes pilus

Has the F plasmid

Sequence of DNA that tells F plasmid where to start making DNA and when to start moving into another cell

Does not have the F plasmid, and receives it from the F+ plasmid which makes it a F+ cell

High frequency of recombination, a type of F+ cell whose plasmid is incorporated into the chromosome

Regions of the same sequence of DNA that can help genetic material zip together (swapping DNA)

Horizontal gene transfer • Recipient cell takes up DNA from the environment • Used for genetic engineering by artificially inducing competence

Not from parent to child, but like sibling to sibling, human to human

Cells that take up DNA

Homologous recombination

Horizontal gene transfer • Using bacteriophage to carry host bacterial DNA to recipient cell, infecting that new cell • Requires homologous recombination

The piece of host bacterial DNA accidentally inserted by the bacteriophage may have genes for antibiotic resistance

Segments of DNA that copy themselves from one location to another in the same or different molecule • Retains original segment at the original site (integrase) • Includes one that encodes transposase

Takes DNA + makes a copy to insert it into another location. That area doesn’t lose the DNA, but makes a copy.