Bacterial Genetics

Glossary

A  B  C  D  E  F  G  H  I  J  K  L  M  N  O  P  Q  R  S  T  U V  W  X  Y  Z

Auxotroph: nutritionally deficient, requires a nutritional growth factor not needed by the wild type prototroph

Allele: one of 2 or more alternate forms of a gene

Bacteriophage: viruses of bacteria. Often referred to as phage.

Clone: a group of cells all descended from a single common ancestor

Competent cells: bacterial cells able to be transformed. Some bacteria are naturally competent, but most need to be treated either with chemicals (salts) or electricity (electroporation) to produce the pores in the cell wall which allow the DNA to enter

Conjugation: the unidirectional transfer of genetic information between cells by cell-to-cell contact. Dependent on transfer function genes or tragenes.

Episome: an older term describing a genetic element which can exist either free (i.e. a plasmid) or as part of the cellular chromosome. Examples include the sex factor (F+) and lysogenic phage DNA

Fertility Factor (F): an episome which determines the sex of a bacterium. The presence of this episome makes the cell male (F+), the absence makes it female (F-)

Gene cassette: a group of related genes carried within an integron, often conferring antibiotic resistance. May also exist in a free circular form, however, the genes within the cassette are promotorless and require capture by an integron to insert into the chromosome.

Genotype: the genetic composition of an organism (as distinguished from its physical characteristics or phenotype)

Hfr (high frequency of recombination): E. coli cells in which the F factor is incorporated into the bacterial chromosome resulting in unusually high frequencies of recombination

Insertion Sequences : mobile genetic elements that encode only functions involved in insertion events, and being comprised only of the transposase gene flanked by repeat sequences. They are the site of insertion of other mobile elements including F factor.

Integron : A mobile genetic element that can capture and carry genes, by site-specific recombination and utilizing the enzyme integrase. Frequently these genes include antibiotic resistance genes, in gene cassettes. An integron may carry one or several gene cassettes.

Mobile genetic element: a DNA sequence which can move from one cell to another.

Mutant: an organism with an inheritable change in the DNA sequence of a gene.
A conditional mutant is one that it is known to display its mutant phenotype only under certain conditions. A particular condition where the mutant phenotype is evident is termed non-permissive, while the wild-type phenotype is observed when conditions are permissive.

Phenotype: the observable properties of an organism

Plaques: round cleared areas on a confluent cell sheet which results from the killing and lysis of the cells by several cycles of virus or phage growth

Plasmid: replicating pieces of DNA, that are stably inherited in an extrachromosomal state i.e. not incorporated into the chromosome

Prototroph: nutritionally wild type

Recombination: results from a mating between two different mating types and displays traits in the offspring which were not found together in either parent. In E. coli, is a function of the recA gene

Transduction: transfer of genetic material from one bacterium to another via a phage particle

Transformation: the introduction of DNA (commonly a plasmid, but also any free DNA in the environment) from an outside source into a bacterium. To be able to be transformed, the cells must be competent

Transposon: a mobile genetic element incorporating an insertion sequence and additional genes, commonly antibiotic resistance genes

Wild type: a form of a gene commonly found in nature – the “normal” form of the gene