Untitled Quiz

Study Notes

Bacterial genetics studies inheritance and variation in bacteria.
All inherited traits are encoded in DNA.
Bacterial nucleic acids include DNA (chromosome and plasmids) and RNA (tRNA, rRNA, mRNA).

A bacterial chromosome is a single, supercoiled, circular double-stranded DNA helix.
Genetic information is stored as a sequence of bases in this molecule.

A gene is a unit of heredity.
A gene is a DNA segment carrying information for a specific biochemical or physiological property.
Genes are carried on the bacterial chromosome.
Genes are essential for bacterial growth.

Definition: Extrachromosomal, small circular, double-stranded helical DNA.
Properties: Do not code for essential bacterial functions for survival. Separate replicon or episome.
Functions:
- Antibiotic resistance (R factor).
- Toxin production.
- Bacteriocins (toxic proteins killing other bacteria).
- Some surface antigens

Observable change in a species.
- Phenotypic variation: Genes are not modified; expression is altered in response to the environment (e.g., sporulation).
- Genotypic variation: Genetic alteration, heritable.
  - Mutation: Alteration of the nucleotide sequence of an organism's DNA. Spontaneous or induced by physical or chemical agents (e.g., heat, radiation, chemicals). Heritable. Types include base substitution, frameshift, insertion, and deletion.
  - Genetic Transfer: Transfer between cells (e.g., transformation, transduction, conjugation) or within same cell (e.g., transposition).

Transposable elements (transposons or "jumping genes") move from one DNA site to another in the genome.
Transposons insert into DNA at random positions.

DNA release from dead cells (lysis) followed by uptake by recipient cells. Recipient cells need to be competent.
Any gene can be transformed.

Bacteriophages (bacteria viruses) act as vectors transferring DNA from donor to recipient bacteria.

Plasmid-mediated mating (joining) of two bacteria.
DNA transfer from a donor to a recipient through direct cell contact and sex pilus formation.
The mating process is controlled by an F (fertility) plasmid, which carries genes for proteins required for mating (e.g., sex pilin).
The process involves the transfer of one strand of the F plasmid. Recipient cell replication results in an F+ cell.
During mating, the pilus of the donor F+ bacterium attaches to the recipient F- bacterium.
F-Plasmid DNA is enzymatically cleaved and transferred across the bridge into the recipient cell.
The process completes with strand synthesis forming a double-stranded F plasmid in both cells.
The recipient cell now can transmit the plasmid.

Successful gene transfer requires recombination, which inserts the transferred genetic element into the recipient's DNA, ensuring inheritance in progeny.