The proposed nomenclatorial system for maize is as follows:

  1. The linkage groups will be designated by Arabic numerals. Group 1 will include those genes which lie in the longest of the monoploid set of 10 chromosomes, etc. The longest chromosome will be called chromosome 1 and the shortest chromosome 10. Arabic numerals will be used for both linkage groups and chromosomes since the Roman numerals are too cumbersome.
  2. Whenever biliteral symbols are used the second letter shall not be dropped as a subscript. Italicize gene symbols.
  3. Literal superscripts shall be used to represent different members of an allelomorphic series, e.g., Rr, Rg, rr, rg.
  4. Numeral subscripts shall be used to represent different genes which give phenotypically similar effects, e.g., v1, v2, v3, etc.
  5. The normal allelomorph of a mutant gene shall be designated by the use of the + sign as a superscript, e.g., the normal allelomorph of sugary (su) will be su+, and not Su or +. The plus sign alone may be used for normal allelomorphs in such genotypic formulae as
    6. + +
    su Tu

    but these allelomorphs should be designated as indicated above when the formula is written as su+ Tu+ / su Tu.

    This suggestion was made by the Drosophila group and we believe it meritorious. It enables one to tell whether the mutant gene is dominant or recessive to the normal or average condition. And, too, the normal gene is nothing more than an allelomorph of the mutant one.

  6. The letter T (italicized) shall denote reciprocal translocations or segmental interchanges. T(1-2)1 would represent the first case of a reciprocal translocation between chromosomes 1 and 2, T(1-2)2 the second, etc. Numeral subscripts instead of literal ones are recommended to denote the different translocations. There are several objections for using a, b, c, etc. to denote the different translocations. When more than 26 different translocations involving the same two chromosomes are found we should be forced to use biliteral subscripts, such as aa, ab, ac, etc. The letters of the alphabet have in the past been used for symbolizing genes. For example, we have designated the different virescents as v1, v2, v3, etc., and not as va, vb, vc, etc.
  7. The symbol Df (italicized) shall be used for Deficiency. For example, the first deficiency involving chromosome 10 will be represented as Df 101; the second as Df 102, etc.
  8. The symbol In (italicized) shall stand for Inversion. An inversion involving chromosome 4 will be represented as In 41; the second one as In 42, etc.
  9. It was decided that there was, as yet, no need to formulate a system of nomenclature for duplications.

This office will do all that it can to enable you to secure any of the stocks listed in this letter but it should be remembered that in several cases the amount of seed is small and we may not be able to fill your request.

Sincerely yours,
M. M. Rhoades
MMR:B

ENCLOSURES