Question

Which of the following phenomena is demonstrated in the above given image?

• A. Polygenic inheritance
• B. Sex-linked inheritance
• C. Incomplete dominance
• D. None of the above

Answer 1

The correct option is A Polygenic inheritance

Polygenic inheritance describes the inheritance of traits that are determined by more than one gene. One wheat variety with a gene for dark red colour that is homozygous dominant is crossed with another variety which has a homozygous recessive gene for white colour. The red colour in the wheat kernel is incompletely dominant over white hence the F${}_1$ hybrid has a kernel intermediate between red and white i.e. medium red. The offspring of the F1 generation are heterozygous dominant for both genes. Thus when F${}_1$ hybrids are crossed to get the F${}_2$ generation the kernel colour has a range dark red, medium dark red, medium red, light red and white in the ratio 1:4:6:4:1. The kernel colour of wheat is determined by two genes R and R${}^{{}^{\prime }}$. The red colour and its shades in the wheat kernel will be determined by homozygous dominant RRR${}^{{}^{\prime }}$R${}^{{}^{\prime }}$ gene expression or heterozygous dominant RrR${}^{{}^{\prime }}$r${}^{{}^{\prime }}$ gene expression.