genetics of bacteria

Genetics of Bacteria

• Bacterial genome =

Genetics of Bacteria

• Bacterial genome = One circular DNA molecule

• E. coli chromosome has 100 times more DNA than in a typical virus, but much less than a eukaryotic cell.

• Packed into nucleoid region of cell

• Plasmid =

Genetics of Bacteria

• Bacterial genome = One circular DNA molecule

• E. coli chromosome has 100 times more Dna than in a typical virus, but much less than a eukaryotic cell.

• Packed into nucleoid region of cell• Plasmid = small circular extra piece of

DNA

Bacterial Genetic Recombination

• What is the main source of genetic recombination in bacteria?

• Mutations

• What are the other sources of recombination?

Transformation

Transduction

What is the vector of

transduction?

Conjugation

Plasmids• What is a plasmid?

• Small circular, self replicating piece of bacterial DNA

• Plasmid genes are advantageous to the bacteria that has them

• Plasmids that confer resistance to antibiotics are called R plasmids

Regulation of Gene expression in prokaryotes (operons)Why is it important that regulation of protein production occur in an organism?

Repressible operons• Repressible operons have structural genes

that code for the production of the substrate (anabolic process).

• The repressor protein is produced in an inactive form, leaving the operator open

• In the presence of the substrate, the substrate will allosterically bind to the repressor protein (is a co-repressor) and activate the repressor protein causing it to bind to the operator

Inducible operons• Inducible operons have structural genes

that produce enzymes that break down a substrate (catabolic process).

• The repressor is translated into its active configuration and will bind to the operator in the absence of the substrate.

• If the substrate is present, it binds to the repressor protein and de-activates it, thereby opening up the operator.

In the lac operon, cAMP acts as a volume control…

What would happen if:

•High glucose, high lactose?

•Low glucose, high lactose?

•High glucose, low lactose?

•Low glucose, low lactose?

Transformation Lab

• Each plate….– What amount of

growth do you expect?

– What is the purpose of the plate (hint: what would be indicated if amount of growth did NOT match expected?)?

• LB plate (-pGLO)• LB/amp plate (-pGLO)• LB/amp plate (+pGLO)• LB/amp/ara plate

(+pGLO)

Ampicillin resistance gene

Gene for regulatory protein for arabinose operon

Modified arabinose operon – genes for enzymes replaced with pGLO gene (codes for glowing fluorescent protein = GFP)