In the course of preparing a list of barley genes (1), it became obvious that many barley workers do not understand how to refer to and distinguish between a gene and its alternate forms, namely alleles. For example, the final sentence of the abstract in a recent article (2) reads "The gene symbol Rsg2b was assigned to this gene; whereas, the gene symbol formerly designated Grb was modified to Rsgla." In fact, Rsg1a and Rsg2b are designations for mutants a and b, one belonging to the gene Rsg1 and the other to the gene Rsg2. Similar examples are frequently encountered in the BGN, see BGN 13:3, 13:9, 13:69, 14:21, 14:71- 74, 14:173, 15:26, 15:29, and 16:32 for examples.
According to the presently accepted nomenclature systems (BGN 1:4, 2:5, 11:1), a new character exhibiting mendelian inheritance is assigned a symbol, let us say in the following theoretical example, sym. Subsequently isolated mutants with similar phenotypes are designated by some workers as sym,,b, sym,,c and by others as sym 2 and sym 3, etc. Assume that four additional sym mutants are identified and subjected to genetic tests with the result that the second and fourth are found to be alleles of the original sym gene while the third and fifth are alleles of another gene. To distinguish between the two sym genes one has to add a gene (locus) designation to the symbol which yields sym1 and sym2 or sym-a and sym-b. In the first system the wildtype and mutant alleles of the gene sym1 are correctly referred to as Sym1, sym1a, sym1b and sym1d and of the gene sym2 as Sym2, sym2c and sym2e. In the second system the wild type and mutant alleles are correctly called Sym-a sym-a1 sym-a2 and syma4, while those of the symb gene are Sym-b, sym-b3 and sym-b5.
Given this rather simple procedure for naming barley genes and their alleles, why is it often used incorrectly? While the existence of two parallel systems for gene and allele designations may be in part responsible, I feel that a primary culprit is the term gene symbol in the Barley Genetic Stocks section of the BGN. Under this heading one finds (i) symbols plus gene designations for some stocks, e.g., msg1 to msg24, (ii) specific alleles of other stocks, e.g., msg25r and msg26u as well as (iii) designations for more than one gene for still other stocks, e.g., btlBt2 and min en-min. Is it not possible to replace the term gene symbol with one accurately describing this mixture, namely genetic constitution?
References:
Søgaard, B. and P. von Wettstein-Knowles: Barley: genes and chromosomes. Carlsberg Res. Commun. 52, in press (1987).
Merkle, 0., J. Webster and G. Morgan: Inheritance of a second source of greenbug resistance in barley. Crop Sci. 27, 241-243 (1987).