Microbial Genetics: Plasmids, Transposons, and Gene Transfer Mechanisms

What are plasmids?

Self-replicating circular pieces of DNA, primarily found in bacteria, can enhance pathogenicity and may code for antibiotic resistance.

What are transposons?

Segments of DNA that can move from one region of DNA to another, potentially inactivating genes and carrying additional genes

What is vertical gene transfer?

The transfer of genes from an organism to its offspring.

What is horizontal gene transfer?

The transfer of genes between cells of the same generation, involving a donor cell and a recipient cell.

What is transformation in bacteria?

The process where genes are transferred from one bacterium to another as 'naked' DNA.

What is conjugation in bacteria?

The transfer of plasmids from one bacterium to another through direct cell-to-cell contact.

What is transduction in bacteria?

The transfer of DNA from a donor cell to a recipient cell via a bacteriophage.

What is generalized transduction?

A process where random bacterial DNA is packaged inside a phage and transferred to a recipient cell.

What is specialized transduction?

A process where specific bacterial genes are packaged inside a phage and transferred to a recipient cell.

How do plasmids contribute to antibiotic resistance?

can encode resistance factors that allow bacteria to survive exposure to antibiotics and can be transferred horizontally.

What role do insertion sequences (IS) play in transposons?

They code for transposase, the enzyme that cuts and reseals DNA during the transposition process.

What is the significance of the recipient cell in horizontal gene transfer?

The recipient cell incorporates part of the donor DNA and becomes a recombinant cell.

What is the difference between Gram-negative and Gram-positive bacteria in conjugation?

Gram-negative bacteria use sex pili for attachment, while Gram-positive bacteria use a sticky substance to hold cells together.

How does replication ensure the passage of genetic information?

DNA polymerase makes only 1 mistake in a billion bases, ensuring nearly faithful passage of genetic information.

What is the impact of horizontal gene transfer on microbial evolution?

allows for rapid genetic variation and adaptation among microbial populations, contributing to evolution.

What is the role of a conjugative plasmid?

allows the donor bacterium to transfer plasmids to a recipient during conjugation.

What happens if a transposon inserts within a gene?

may inactivate the gene, disrupting its function.

What is the size comparison of plasmids to bacterial chromosomes?

Plasmids are 1 to 5% the size of a bacterial chromosome.

What is a recombinant cell?

A recipient cell that has incorporated donor DNA through horizontal gene transfer.