Since Mendel 1855-56; Genetics teaches that genes can dominate one another. This was based on purely qualitative genetic analysis. This article just says that only quantitative genetic analysis can show the reality behind gene interaction. Enzymes that carry on gene actions do not act qualitatively. Instead, Enzymes act quantitatively and the results show that there is no such thing as a dominant or recessive gene. genee
Genes control the manifestation of biological traits that appear in individuals as phenotypes via the activity of enzymes, proteins having catalytic proprieties. Genes can be transcribed into various types of RNA (transfer RNA or tRNA, messenger RNA or mRNA, ribosomal RNA or rRNA, and less studied regulator RNA). Genes that govern phenotypes directly are structure genes that are transcribed only into mRNA carrying the plans of proteins (some being just structural proteins, many being enzymes and some others hormones like well-known insulin) that get synthesized within ribosomes.
In the simplest cases, each enzyme thus made through protein synthesis catalyzes a chemical reaction by transforming a certain amount of a source molecule (the substrate) into a certain amount of a new molecule called Product of the reaction. So an enzyme action has both a qualitative aspect (the type of substrate it acts on and/or the type of product it produces) and a quantitative aspect (the amount of substrate it is able to transform and/or the amount of product it can produce). For some reasons, Geneticists often only consider the qualitative aspect of enzyme action and at the same time gene action, oblivious of the quantitative aspect of enzyme or gene action that is always present. The principle of a gene dominating another gene came from this partial interpretation of gene action deriving from enzyme action. When the quantity of the product of an enzyme action is taken into account, which automatically includes the qualitative aspect, then it becomes obvious that no gene can dominate another which is supposed to be recessive.
Let us look at the real gene effect behind the seed color of Peas studied byMendel (1822-1884), the Father of Genetics. There are two alleles, one Y1 producing let say a unit of yellow pigment, and the second Y0 producing no unit of yellow pigment. There are two homozygotes Y1Y1 and Y0Y0, the former with yellow seeds because of the pigment synthesized and the later with green seeds because when in some plants no pigment (other than green) is produced the organ (here the seed of the Pea) will be just green like the leaves. In cereals the non colored seed will be white because of the white starch it contains. In Pea, the default color is green. If a plant organ wants to be colored otherwise, it has to do some extra work : the synthesis of the desired pigment, the yellow pigment in this case.
The homozygote 1 has the genotype Y1Y1 (made of 2 alleles) produces two units (1+1, each from each allele) of yellow pigment and has a phenotype that is qualitatively yellow seeds and quantitatively intense yellow seeds.
The homozygote 2 has the genotype Y0Y0 produces zero unit of yellow pigment and has a phenotype that is both qualitatively and quantitatively green seeds.
The heterozygote has the genotype Y1Y0 produces one unit (1+0) of yellow pigment and has a phenotype that is qualitatively yellow seeds and quantitatively yellow (non intensive yellow) seeds, so quantitatively different from that of the homozygote1 and thus no dominance is any more involved here.
It means that when you cross both homozygotes (Y1Y1 and Y0Y0) you get a heterozygote Y1Y0 with yellow seeds indeed because of the action of one Y1 allele action. If you look only at the color yellow you will say that both the homozygote Y1Y1 and the heterozygote Y1Y0 have the same phenotype (yellow seeds) and thus the allele Y1 appears to be dominant over the allele Y0. But this is only a partial interpretation of the reality. How about the amount of yellow pigment synthesized in each case, does it count for nothing ? Why ? The whole interpretation clearly shows that the heterozygote fully resembles none of its parents. Its phenotype is in between those of its parents. stylowakobieta
From the above data it can be seen that 1+1 = 2 is different from 1+0 =1 and thus the heterozygote does not have the same phenotype as the yellow seed homozygote. Also 1 + 0 = 1 does not mean that 1 dominates 0. It just does not make any sense to say that. So there is no dominance in the expression of the phenotype of the hybrid Y1Y0.