1. In naming hereditary factors, the use of languages of higher internationality should be given preference.
2. Symbols of hereditary factors, derived from their original names, should be written in Roman letters of distinctive type, preferably in italics, and be as short as possible.

   AMENDMENT: The original name should be as descriptive as possible of the phenotype. All gene symbols should consist of three letters.
   COMMENTS: All new gene symbols should consist of three letters. Existing gene symbols of less than three letters should be converted to the three letter system whenever symbols are revised. When appropriate, one or two letters should be added to existing symbols.

3. Whenever unambiguous, the name and symbol of a dominant begin with a capital letter and those of a recessive with a small letter.

   AMENDMENT: When ambiguous (co-dominance, incomplete dominance, etc.) all symbols should consist of a capital letter followed by two small letters that designate the character, a number that represents a particular locus, and a letter or letters that represents a particular allele or mutational event at that particular locus.
   COMMENTS: As an example, the letter Mdh can be used to designate the character malate dehydrogenase, Mdhl would represent a particular locus for malate dehydrogenase and Mdhla, Mdh1b, Mdh1c, etc. would represent particular alleles or mutational events at the Mdhl locus.

4. Literal or numeral superscripts are used to represent the different members of an allelic series.

   AMENDMENT: All letters and numbers used in symbolization should be written on one line; no superscripts or subscripts should be used.

5. Standard or wild type alleles are designated by the gene symbols with a + as a superscript or by a + with the gene symbol as a superscript. In formulae, the + alone may be used.

   AMENDMENT: This rule will not be used in barley symbolization.

6. Two or more genes having phenotypically similar effects are designated by a common basic symbol. Non-allelic loci (mimics, polymeric genes, etc.) are distinguished by an additional letter or Arabic numeral either on the same line after a hyphen or as a subscript. Alleles of independent mutational origin may be indicated by a superscript.

   AMENDMENT: Barley gene symbols should consist of three letters that designate the character, a number that represents a particular locus, and a letter or letters that represents a particular allele or mutational event at that particular locus. All letters and numbers should be written on the same line without hyphens or spaces. Alleles or mutational events that have not been assigned to a locus should be symbolized by three letters that designate the character followed by two commas used to reserve space for the locus number when determined, followed by a letter or letters representing the particular allele or mutational event. After appropriate allele testing, the correct locus number will be substituted for the commas. Where appropriate (when assigning new symbols or when revising existing symbols) letters representing alleles or mutational events should be assigned consecutively without regard to locus number or priority in discovery or publication.
   COMMENTS: The use of the proposed system of symbolization can be illustrated by the desynaptic mutants. Two loci are known: lc on chromosome 1 and ds on chromosome 3. These will be resymbolized as desla and des2b. A large number of desynaptic mutants have been collected. They will be designated des,,c, des,,d, des,,e, etc. If allele tests show that des,,c is at a different locus than desl and des2, des,,c will become des3c. If allele tests show that des,,d is at the same locus as des2, des,,d will become des2d. In practical use, the symbol des will be used when speaking of desynapsis in general or if only one locus was known for the character. The symbol des2 will be used when speaking of that particular locus, and the symbol des2b will be used only when speaking of that particular allele or mutational event. If additional designation is needed in particular symbolization, it can be obtained by adding numbers behind the allele letters, and, if still further designation is needed, letters can be added to the symbol behind the last number. Symbolization consisting of alternation of letters and numbers written on the same line without hyphens or spaces will allow for the expansion of the symbol as future needs arise.

7. Inhibitors, suppressors, and enhancers are designated by the symbols I, Su and En, or by i, su and en if they are recessive, followed by a hyphen and the symbol of the allele affected.
8. Whenever convenient, lethals should be designated by the letter l or L and sterility and incompatibility genes by s or S.

   AMENDMENT: This rule will not be used in barley symbolization.
   COMMENTS: J. G. Moseman, BGN 2:145-147, proposed that the first of the three letters for designating genes for reaction to pests should be R. The second and third letters will be the genus and species names of the pest.

9. Linkage groups and corresponding chromosomes are preferably designated by Arabic numerals.
10. The letter X and Y are recommended to designate sex chromosomes.
11. Genic formulae are written as fractions with the maternal alleles given first or above. Each fraction corresponds to a single linkage group. Different linkage groups written in numerical sequence are separated by semicolons. Symbols of unlocated genes are placed within parenthesis at the end of the formula. In euploids and aneuploids, the gene symbols are repeated as many times as there are homologous loci.
12. Chromosomal abberations should be indicated by abbreviations: Df for deficiency, Dp for duplication, In for inversion, T for translocation, Tp for transposition.
13. The zygotic number of chromosomes is indicated by 2n, the gametic number by n and basic number by x.
14. Symbols of extra-chromosomal factors should be enclosed within brackets and precede the genic formula.

Recommendation from Genetics IV:959-962 on gene and mutation designations were as follows:

1. Present designations for genes and mutations. - Most of the present designations should be maintained. However, new designations may be given, when additional information indicates that new designations would aid in the identification of genes and mutations.
2. New designations for genes and mutations. - New genes or mutations will be designated by characteristic, locus, allele, and then the order of identification or mutational event. Three letters will be used to identify new characteristics. Consecutive numbers will be used to identify the order of identification or mutational even. Loci will be designated by numbers and alleles by letters when they are identified. For example des-6 indicates that this is the sixth gene or mutation identified for the characteristic des (desynaptic), and desl-6 and des2-7 indicates that gene or mutational events 6 and 7 for the desynaptic characteristic have been shown to be at different loci and those loci are then designated 1 and 2, respectively. Also, desla6 and des1b8 indicate that the gene or mutational events 6 and 8 for the characteristic desynaptic have been shown to be at different alleles at locus 1 and those alleles are then designated a and b.

Publication in BGN of the recommended system for nomenclature and gene symbolization for barley was suggested at the Fifth IBGS (BGN 17:1-5). Use of Ml as the designation of genes for resistance to powdery mildew was recommended durinq the workshop.

Penny von Wettstein-Knowles, Department of Physiology, Carlsberg Research Laboratory, Gamle Carlsberg Vej 10, DK-2500 Valby, Denmark, has agreed to coordinate assignment of new gene symbols for barley.