Chapter 7: microbial genetics

What is gene transfer

Exchange of nucleotide sequences

(One organism picking DNA up)

Recombinant

cells with DNA molecules that contain new nucleotide sequences

Contain new DNA

How does gene transfer among prokaryotes work?

Vertical gene transfer or Horizontal gene transfer

vertical gene transfer

Passing of genes to the next generation (both eukaryotes, prokaryotes, and even us)

Horizontal gene transfer

Donor cell contributes part of genome to recipient cell

Only protected by bacteria within some generation

What are the three types of horizontal gene transfer

Transformation

Transduction

Bacterial conjugation

Transformation

Recipient cell taking DNA from environment and being able to express it

Transduction

Transfer of DNA from one cell to another via replicating virus

Involves virus specific to bacteria

Bacteriophage or phage

What must the virus be able to do in transduction?

Infect both donor and recipient cells

What can result once the virus is able to do this?

Transfer of antibiotic resistance and toxin genes

What happens in generalized transduction?

Transducing phage carries random DNA segment from donor to recipient

What happens in specialized transduction?

Only certain donor DNA sequences are transferred

What toxins are associated with specialized transduction

Scarlet fever, E.coli 0157;H7, diphtheria

Conjugation

Genetic transfer requires physical contact btwn donor and recipient cell

Donor cell remains alive

Mediated by conjugation (sex) pili