Question

What role does DNA play in phenotypic expression in organisms?

Answer 1

The DNA is made up of genes, which are made up of alleles which are present on the locus of the chromosomes. The phenotypic expression in organisms depends upon the effect of genes and their expression. The genes can be dominant or recessive. The expression of genes can be controlled by various mechanisms like ---1)epistasis 2)supplementary genes 3)complementary genes .4)duplicate genes.

The phenotypic expression can be controlled by the above mentioned mechanisms. The phenotypic expression is the external available characteristic expression of the organism under study which can be seen.

1)epistasis-it is a mechanism where the effect of one gene is hindered or modified by the effect of the other gene.

2)complementary genes--In mechanism phenotypic expression and colour is expressed when both the genes are in the dominant state and if one gene is in the dominant state then the colour is changed example in flowers of garden pea. In this when both the genes are in dominant state then the colour of flower is purple-AABB,AaBb,AABb, AaBb. The colour of flower is white when one of the gene is in recessive state example--Aabb,aaBB,AAbb,aaBb,aaBB.

3)supplementary genes--In this mechanism, one dominant gene has one particular expression, other dominant gene has other particular expression, and when both the genes are dominant then a new phenotypic genetic expression is there example--colour coat in mice, CCaa--colour coat colour is black, ccAA-colour coat is albino, and in CCAA or CcAa--in this phenotypic expression is agouti.