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1. Recommended Rules for Gene Symbolization in Wheat
(Adapted from the International Rules of Genetic Nomenclature)
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 italics, or in Roman letters of distinctive type.
3. Whenever unambiguous, the name and symbol of a dominant should begin with a
capital letter and those of a recessive with a small letter (see also special
rules for symbolizing biochemical and DNA loci and host:pathogen/pest systems).
4. All letters and numbers used in symbolization should be written on one line;
as far as possible no superscripts or subscripts should be used.
5. The plus sign (+) will not be used in symbolization of hereditary factors in
wheat.
6. Two or more genes having phenotypically similar effects should be designated
by a common basic symbol. Non-allelic loci (mimics, polymeric genes, etc.) will
be designated in accordance with two procedures:
(i) in sequential polymeric series where an Arabic numeral immediately follows
the gene symbol; e.g., Sr9.
(ii) in orthologous sets where the basic symbol is followed by a hyphen ("-")
followed by the locus designation taking the form of the accepted genome symbol
and a homoeologous set number represented by an Arabic numeral; e.g., Adh -A1
designates the A-genome member of the first Adh set. Different alleles,
or alleles of independent mutational origin, are designated by a lower-case Roman
letter following the locus number designation; e.g., Sr9a, Adh-A1a. (See
also guidelines for nomenclature of biochemical and DNA loci).
6.1 Temporary symbol designations: Where linkage data are not available, provision
has been made for temporary symbols. These shall consist of the basic symbol followed
by an abbreviation for the line or stock and an Arabic number referring to the
gene; e.g., SrFr1, SrFr2, etc., refer to two genes for reaction to Puccinia
graminis in cultivar Federation. It is recommended that official records
of temporarydesignations be kept, but it is not essential that subsequent numbers
from other laboratories (e.g., SrFr3) be checked against earlier numbers either
phenotypically or genetically.
7. Inhibitors, suppressors, and enhancers are designated by the symbols L So,
and En, or by i,su, and en if they are recessive, followed by a space and
the symbol of the allele affected.
8. In wheat and related species, linkage groups and corresponding chromosomes
are designated by an Arabic numeral (1-7) followed by genome designated by a capital
Roman letter; i.e., for hexaploid wheat of group aestivum (Morris and Sears (1038)),
1A-7D. This system supersedes the original designations using Roman numerals;
i.e., I-XXI. The designations for homoeologous group 4 chromosomes of wheat are
as agreed at Workshop 1, 7th International Wheat Genetics Symposium, Cambridge,
UK (see Proceedings, Miller TE & Koebner RMD eds. pp. 1205-1211); that is,
the previously designated chromosome 4A was redesignated 4B and the previous 4B
was redesignated 4A. Consequently, the former 4AS became 4BS and the former 4AL
is 4BL. Likewise, the former 4BS and 4BL were redesignated 4AS and 4AL, respectively.
Chinese Spring is accepted as having the standard chromosome arrangement. Chromosome
arms (or telocentric chromosome derivatives) are designated S (short), L (long),
on the basis of relative arm length within the chromosome. In the case of equal
arms they are arbitrarily designated S or L on the basis of homoeology with the
short or long arms of the other chromosomes of their homoeologous group (see Workshop
I Proceedings of the 7th International Wheat Genetics Symposium).
9. Genetic formulae may be written as fractions, with the maternal alleles given
first or above. Each fraction corresponds to a single linkage group.
10. Chromosomal aberrations should be indicated by the abbreviations Df for deficiency,
Dp for duplication, In for inversion, T for translocation, and Tp for transposition.
In wheat there are a number of genes derived from related species by introgression.
Such genes in different instances reside at different locations. One location
maybe taken as standard. Other locations will be considered as transpositions
relative to a designated standard. When a gene does not reside in its standard
chromosome position, the new chromosome designation maybe given in brackets following
the gene designation; e.g., Hp (To 6D) refers to a line carrying the introgressed
"hairy neck" gene on chromosome 6D instead of 4B which is taken as standard. Alternatively,
the chromosome involved may be described as a translocation. Guidelines for the
description of translocated chromosomes both within wheat, and between wheat and
alien chromosomes are provided in (705).
11. The zygotic number of chromosomes is indicated by 2n, the gametic number by
n and the basic number by x.
12. Symbols for extra-chromosomal factors should be enclosed within brackets and
precede the genetic formula.
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