Q.Explain polygenic inheritance with an example.

Step 1. Polygenic inheritance is the pattern in which a group of genes, rather than a single gene, together determine one trait, with each gene's alleles contributing additively rather than one masking another.

Step 2. Swedish geneticist H. Nilsson-Ehle demonstrated this in 1909 using wheat kernel colour, controlled in his experiment by two genes, each with two alleles (dominant red versus recessive white at each locus); crossing dark red (R1R1R2R2) with white (r1r1r2r2) gave a medium-red F1 (R1r1R2r2).

Step 3. In the F2, kernel colour intensity tracked directly with the number of 'R' alleles present - four R alleles gave dark red, three gave medium-dark red, two gave medium red, one gave light red, and zero gave white - so each dose of the R allele added a set increment of red pigment, in a straightforwardly additive way. …

Define polygenic inheritance and walk through Nilsson-Ehle's additive-dose …

• Confusing polygenic inheritance (many genes, one trait) with multiple alleles (many forms of one gene). …