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• Episomes = plasmids that can reversibly

incorporate into the bacterial chromosome

• Plasmid genes are advantageous to the bacteria that has them

• Plasmids that confer resistance to antibiotics are called R plasmids

Transposons

• Jumping genes

• Does not depend on complementary base pairing between homologous regions of the chromosome.

• Transposons move to regions that the gene has never been

Transposase recognizes the inverted repeats

Targeted inverted

repeats are cut, and the target is cut, then the transposon is

inserted

Composite transposons move extra genes along with the inserted sequence,

and are very beneficial to the bacteria

Regulation of Gene Expression

Regulatory gene = codes for regulatory protein

Regulatory protein = binds to the operator and stops transcription of the structural geneOperator = on /off switch for transcription of structural gene

Repressible operons• Repressible operons have structural genes

that code for the production of the substrate.

• 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 sturcutral genes

that produce enzymes that break down the substrate.

• 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.

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As the lactose is degraded by the new enzymes, the regulatory protein once again binds to the operator

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