Genetics of Bacteria and Their Viruses

Flashcards about bacterial genetics, covering topics like bacterial DNA, gene transfer, and bacteriophages.

Shape and Size of Bacteria

Differ strongly between different species, range in size from 200 nm to 500 µm, lack a nucleus, mitochondria, or chloroplasts, and most have a cell wall.

Nucleoid

The bacterial chromosome, usually circular and around 4-5 Mb of DNA in most studied bacteria. Compaction occurs due to loop formation and supercoiling without nucleosomes. It contains many genes important for metabolism.

Plasmids

Circular DNA molecules that replicate independently of the bacterial chromosome, often carrying antibiotic resistance genes and used as gene transfer vectors in genetic engineering.

Pangenome

Describes all the genes found in any E. coli strain ever sequenced, consisting of approximately 15000 different genes.

Transposable Elements

DNA sequences that can jump from one position to another or from one DNA molecule to another. They can lead to deletions and inversions of the bacterial chromosome.

Transposons

Transposable elements in bacteria that contain one or more genes unrelated to transposition that can be mobilized along with the transposable element.

Transformation

Process where donor cell releases DNA into the medium and donor DNA is taken up by the recipient, changing the genetic code of the bacterium.

Cotransformation

Genes located close together being transferred as a unit to the recipient cell. Used to map gene order, where closer genes are more likely to be transferred together.

F (fertility) Factor

A conjugative plasmid transferred from cell to cell by conjugation. It is a low-copy-number plasmid ~100 kb in length and is present in 1–2 copies per cell.

Conjugation

A process in which DNA is transferred from a bacterial donor cell to a recipient cell by cell-to-cell contact, mediated by a pilus.

F+

Cells that contain the F plasmid and are donors in conjugation.

F-

Cells lacking F plasmid and are recipients in conjugation.

Hfr Cells

Are High frequency recombinant cells that; are formed when an F plasmid integrates into the bacterial chromosome through recombination between IS elements

Interrupted Mating Experiments

Experiments which allow researchers to investigate gene orders on bacterial chromosomes through interrupted mating experiments

Lytic Cycle of Phages

Phage DNA enters the cell and replicates repeatedly, cell ribosomes produce phage proteins, phage DNA and proteins assemble, and bacterium is split open (lysis), releasing phage progeny.

Transduction

Bacterial DNA is transferred from one bacterial cell to another by a phage.

Generalized Transducing Phage

Phage transfers DNA derived from any part of the bacterial chromosome.

Specialized Transducing Phage

Phage transfers genes from a particular region of the bacterial chromosome.

Lysogenic Cycle of Phages

No progeny particles are produced, the infected bacterium survives, and phage DNA is transmitted to each bacterial progeny cell when the cell divides

Prophage

The inserted DNA of a phage in the bacterial chromosome during the lysogenic cycle.

Lysogen

Surviving bacterial cell during the lysogenic cycle.