FUNDAMENTALS OF BACTERIAL GENETICS NOMENCLATURE BACTERIAL GENETICS MODULE

GENOTYPE – the genetic constitution of an organism.

Each bacterial gene receives a three-letter designation, which is italicized (or underlined) and written using all lowercase letters. The three-letter designation typically is an abbreviation that relates to the relevant mutant phenotype or metabolic pathway.

ara or ara.

In order to distinguish among different genes in a single pathway, an uppercase letter follows the three-letter designation. Mutations that influence distinct genes in the arabinose utilization pathway are designated –

araA-, araB-, araC- or araA-, araB-, araC-.

Different alleles of a single gene are distinguished from one another with a unique number following the three-letter designation. For example, the alleles of the araA gene are designated –

araA1, araA2, araA3 or araA1, araA2, araA3.

Deletion mutants are identified using the ∆ symbol. For example, a specific deletion mutation in the araA gene might be represented as –

∆ araA109.

Insertion mutants are identified using the “::” symbol. For example, you may have recovered a Tn10 insertion in the araC gene during this module. This insertion mutation would be designated –

araC::Tn10 or araC::Tn10.

Superscripts are used to reveal additional information about a specific mutation. For example, a kanamycin-resistant mutation is designated -

KanR or KanR.

PHENOTYPE – the properties exhibited by a wild-type or mutant organism. In order to distinguish the phenotype of a specific bacterial strain from its genotype, the identical three-letter designation representing the genotype is used. However, the difference is that the phenotype begins with an uppercase letter. And the phenotype is neither italicized nor underlined. During this module, for example, the phenotype of the mutants generated that can’t use arabinose were designated –

Ara-. The “minus” superscript following the phenotype designation indicates the inability to utilize arabinose. Alternatively, a wild-type strain that can utilize arabinose is designated –

Ara+.

The “plus” superscript indicates the ability to utilize arabinose. Conditional phenotypes also are designated using an appropriate superscript. For example, a strain with a temperature sensitive phenotype that only can use arabinose within a specific temperature range is designated –

Arats. PROTEIN Proper nomenclature for proteins exists as well. For example, the protein encoded by the araC gene is designated –

AraC.

Note that the first letter is uppercase and the protein name is neither italicized nor underlined. Additional information regarding the nomenclature of bacterial genetics can be found at –

http://en.wikipedia.org/wiki/Bacterial_Genetic_Nomenclature

ADDITIONAL RELEVANT DEFINITIONS Wild-type – an organism that exhibits a defined phenotype assigned by the researcher. Mutant – an organism exhibiting some altered property or altered phenotype. Mutation – a change in DNA/nucleotide sequence that causes a mutant phenotype.