Q.Give an account on bacterial genetics.

Bacterial genetics is the study of how genetic information is organised, transferred, and expressed in bacteria, centred on the bacterial chromosome, plasmids, and three natural mechanisms of gene transfer.

Bacterial genome organisation

• Bacteria lack a true nucleus; their genetic material is a single, circular, double-stranded DNA chromosome condensed into a region called the nucleoid.
• Many bacteria additionally carry plasmids -- small, circular, extrachromosomal DNA molecules that replicate independently of the chromosome and often carry non-essential but useful genes (e.g., antibiotic resistance genes on R-plasmids, fertility genes on the F-plasmid).

Mechanisms of genetic transfer (recombination)

1. Transformation -- a recipient bacterium takes up naked, fragmented DNA released by a lysed donor cell directly from the surrounding medium and incorporates it into its own genome. Griffith's classic experiment with Streptococcus pneumoniae (dead virulent S-strain transforming live avirulent R-strain into virulent bacteria) first demonstrated this.
2. Conjugation -- a form of 'bacterial mating' in which a donor cell carrying the F-plasmid (F+) forms a sex pilus that connects to a recipient (F-) cell, and a copy of the plasmid (sometimes with chromosomal genes, in Hfr strains) passes directly through this bridge into the recipient.
3. Transduction -- a bacteriophage (bacterial virus) that has accidentally packaged bacterial DNA instead of, or along with, its own genome during a previous infection cycle introduces this DNA into a new host bacterium when it infects it (generalized transduction: random DNA; specialized transduction: genes near the phage's integration site).

Significance …