Rules of Nomenclature
1. The chromosomes are given numbers corresponding to their length as measured visually. The longest chromosome is chromosome 1 the next longest is chromosome 2, and the shortest is chromosome 12.
2. When the work of identifying linkage groups with chromsomes is sufficiently far advanced that all groups can be referred to a definite chromosome, the linkage groups should be renumbered so that the linkage groups bear the same number as their respective chromosomes. In the meantime it is suggested that linkage groups continue to be designated by Roman numerals and chromosomes by Arabic numerals. For the present, the term chromosome linkage group should be reserved for only those cases which have been definitely established. Thus, chromosome 2 and linkage group I are identical (Barton, 1950) and will be designated chromosome linkage group 2(I) when using the combined term, or simply as linkage group I when the chromosome is not mentioned.
3. Gene symbols should be limited to one or two letters and be descriptive. The mutant name is suggestive of the main diagnostic feature and is preferably a simple descriptive adjective or noun, The symbol preferably starts with the initial letter of the mutant name and is followed by the second letter of the mutant name, or by a suggestive letter from the rest of the name.
4. Dominance or recessiveness of a mutant gene should be indicated by comparison with a "standad" or "normal" tomato type. The variety Marglobe is proposed as this normal type, since it is widely grown and is typical of the general concept of the normal tomato morphology.
A mutant gene which is dominant to the normal type is written with the initial letter of the mutant name and symbol capitalized, while one which is recessive to the normal is written with the initial letter in small print. The normal allele of the mutant gene is written with the symbol of the mutant gene followed by the superscript, "+". Thus the normal allele of sp is sp+ and of the mutant Wo is Wo+. A dominant gene appearing later at the sp locus would be designated \sp\D. When it is clear in the text which gene is concerned, the normal allele may be designated simply by the "+" symbol.
5. When new mutants are found which are indistinguishable phenotypically from other mutants previously described, these mutants may be indicated by the name or symbol of the original mutant followed by a numerical subscript, the original mutant being assigned the subscript "l". This has already been done in the case of ms\1\, ms\2\, etc.
6. Translocations are designated by the letter T. The chromosomes involved in the translocations are designated by numbers which refer to dual chromosomes. In order to distinguish between different translocations involving different chromosomes, letters may be used following the chromosome number, as T 1-2a, T 1-2b, etc.
7. Deficiencies are designated by the symbol Df, while the chromosome in which the deficiency occurs is indicated by a numeral corresponding to the chromosome. To distingiish different deficiencies in the same chromosome, numerical subscripts are used.
8. Inversions are designated by the symbol In, and are indicated in the same manner as deficiencies (7 ) above.
9. In order to distinguish between gene symbols and symbols of translocations, deficiencies and inversions, the symbols of genes are italicized.
The purposes of the above rules are simplification and standardization of tomato gene nomenclature. After obtaining reasonable evidence for the existence of a new gene, the discoverer should select an appropriate name and symbol. Symbols that have been published in the TGC reports or elsewhere should never be knowingly applied to other mutations. It is suggested that a complete description of a new mutant gene, with its symbol, should be published in a formal journal or included in the TGC report. Seed should also be made available for any member to check this character with similar mutants in his own possession.
The known mutants and their recognized symbols will be included in the next TGC report. Established symbols with no synonyms will be left unchanged even though they may not conform with the above rules.
______________________________________________________________________________
Time did not permit us to resolve completeLy all of the rules in this list before preparation of the present report. Furthermore, it was impossible to communicate satisfactorily with Dr. Jenkins, who is now on leave in Latin America. It should be pointed out that the comittee is in agreement in respect to all of the rules except No. 4. The opposing viewpoint favors the system now in vogue, utilizing capital or small-case letters to designate the normal allele. The argument presented for these two systems are briefly as follows:
In favor of the capital-small-case symbols now in use:
1. The genes in most of the tomato literature are symbolized in this fashion, and are understood by horticulturists and others who need to use our findings.
2. The use of superscripts is awkward, and until more than two alleles are known for a locus, they would not be needed in this system.
In favor of the system recommended in Rule 4 above:
1. This system provides a clear designation of the normal allele, which is not possible in the other system. A gene symbol without the accompanying "+" invariably indicates a mutant conditioon.
2. It is more convenient and leads to less error in oral exchange and in script records.
Correspondence concerning these rules is invited. A final revised list will appear in the next Report.
Committee on Nomenclature
D. W. Barton, Chairman
L. Butler
J. A. Jenkins