Genetic Terminology

1. Specified traits, phenotypes, are designated by three-letter codes representing the description of the trait. The first letter of the code is capitalized. Letters of the code are not italicized or underlined. Similar traits determined to differ in inheritance and having the same descriptive code, are distinguished by an additional number, e.g. Ygr3 and Ygr7 designate yellow green plants conditioned by different genotypes.

2. Phenotypic traits having varying degrees of expression may be designated by numbers on a scale of 0-9 in parentheses, to indicate the degree of expression, with 1=very low and 9=very high. e.g. Pan(8) indicates high expression of purple anthocyanin pigment.

The description of the degree of expression of variable traits can be given as follows, using for an example the expression of purple anthocyanin and hairiness. For scaling of hue and intensity, comparator charts or visual estimators may be useful.
0 = trait absent Pan(0) = no anthocyanin Hir(0) = no hairs
1 = very low expression Pan(1) = very light purple Hir(1) = 0-1 hairs
2 = low expression Pan(2) = light purple Hir(2) = very few hairs
3 = moderately low expression Pan(3) Hir(3) = few hairs
4 = <intermediate expression Pan(4) Hir(4)
5 = intermediate expression Pan(5) = purple Hir(5) = moderate # hairs
6 = > intermediate expression Pan(6) Hir(6)
7 = moderately high expression Pan(7) Hir(7)
8 = high expression Pan(8) = intense purple Hir(8) = many hairs
9 = very high expression Pan(9) = very intense purple Hir(9) = very many hairs

0-5 = trait variable in expression among individuals Pan(2-5) = Pan variable among individuals  


3. Quantifiable variation within a trait may be designated as statistical estimates of mean (x), standard deviation (s), range (r) and population size (n). It may be important to specify environmental parameters when describing quantifiable variation. e.g. Hair number, Hir, on the margin of the first true leaf, Hir (n=48, x=15, s=4, r=27) Environment, standard growing conditions.

4. The genotype of a specified phenotype is designated in lower case italics (underlined if hand written) using the same three letters, and numbers, of the corresponding phenotype. e.g. ygr3 = ygr3 = genotype of phenotype Ygr3.

5. Alleles are designated by a dash followed by a number, ygr3-1. If no allele is specified, it is assumed to be allele 1, i.e. ygr3-1 is ygr3.

6. Wild type is designated with specified genotype code, all capitalized in italics. E.g. Wild type of ygr3 is YGR3. Alternatively the wild type is designated with a plus (+) symbol associated (following or preceding) the designated code. E.g. wild type of ygr3 is ygr3+, or in a cross with wild type, ygr3/+ or +/ygr3.

7. Segregation of a specified genotype in a progeny is designated by a minus, (-) symbol following the genotypic code. E.g. ygr3- or ygr3/- , indicates that any individual in the segregating progeny may or may not express the genotype.

8. When crosses are specified, the gametic contribution of the maternal parent always precedes the paternal and is separated from the paternal contribution by a slash, (/ ) e.g. female/male, YGR3/ygr3 = heterozygote from wild type female x ygr3 male. Alternatively, +/ygr3.

9. Uniparentally (cytoplasmic) inherited traits are enclosed in parentheses, e.g. (Var) describes a maternally inherited variegated phenotype.

10. Phenotypic and genotypic codes for similar traits in different Brassica species may be the same, and are numbered independently for each species, e.g. ygr3 in B. rapa and ygr3 in B. oleracea.

11. In Brassica, when interspecific crosses are made between stocks with specified traits, e.g. ygr1 and ygr2, cytoplasmic and nuclear genomic symbols (not italicized) are given (see section 2 above), followed by the trait descriptive code. The female is specified with the cytoplasmic genomic symbol, in upper case, together with the nuclear genomic symbol, in lower case, followed by the trait descriptive code. The male is specified by the nuclear genomic symbol, in lower case, followed by the trait descriptive code. E.g. Aa ygr1 x c ygr2 = Aa ygr1 / c ygr2 is a cross between a yellow green B. rapa mother (Aa ygr1) and a yellow green B. oleracea father (c ygr2).