additive genes

additive genes

those in which more than one gene controls a character, with each allele making a definite and measurable contribution towards the character; there is no DOMINANCE between alleles of one gene and no EPISTASIS between different loci (see LOCUS). Many pigment systems are controlled by additive genes, producing a wide spread of variability.
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The GCA and SCA affirm that GCA estimates are owned to additive genes whereas SCA are owned to dominant type of genes.
However, it is important to point out that, although the averages of the squares of the non-additive effects for resistance to Xap prevail, the significance and magnitude of the mean squares of the additive effects in the analysis of variance demonstrated higher influence of additive genes in the response to CBB (Table 2), increasing the possibility to achieve genotypes highly resistant to CBB in advanced generations.
Also, bi-parental mating and inter-mate desirable segregates, beside suitable selection to accumulate favorable additive genes could be the proposed methods for improving salt tolerance in safflower.
Specific combining ability estimates ([[??].sub.ij]) measures the effects of non additive genes (CRUZ & REGAZZI, 1994), and some of them had outstanding negative values both 14th-severity and AUDPC (Table 3).
Hence, these characters need to be given more importance while selecting the breeding lines as they are controlled by additive genes. Therefore, selection based on the characters, both yield attributes (number of productive tillers) as well as nutritional quality traits such as protein, fat, phytate phosphorus, calcium, iron and zinc content having high heritability coupled with high genetic advance as per cent of mean may bring about the desired improvement in yield as well as nutritional quality of pearl millet genotypes.
Additive gene action: Additive genes are those in which members of a gene pair have equal ability to be expressed.
Combining additive genes for slow rusting type resistance to leaf and stripe rusts in wheat, p.
(2010) found significance of GCA and SCA suggesting the importance of additive as well as dominant genes, nevertheless the ratio of GCA/SCA was greater than the unity further indicating the preponderance of additive genes over the dominant ones in the inheritance of seed cotton yield, seed index and lint%.
Proposition 3.--Cyclical selection for a trait controlled by two additive genes with equal effects resulting in sign-concordant environment leads to the following behavior of the system trajectories: in minus-concordant environment any trajectory with [x.sub.2] = [x.sub.3] at the initial state comes to the set [x.sub.1][x.sub.4] = 0 and [x.sub.2][x.sub.3] = 0.
Although both additive and dominance gene action were found significant in cross PS-Pop-1-1-4 x BD-Pop-1-2-3-3 but the magnitude of dominance was higher than additive genes, showing that trait can be exploited for hybrid production effectively.
The greater values of inbreeding depression revealed that dominant or over dominant genes with decreasing effect advocated the expression of days to initial flowering, while less inbreeding depression in some [F.sub.2] hybrids may be due to additive genes or incidence of trangressive segregants.