Why the ratio in pleiotropy is 2 :1 Explain it with example.

Explanation

(i) Pleiotropy :
1. When a single gene controls two .or more characters (traits) it is called pleiotropy/pleiotropism. The gene is called pleiotropic gene.2. As per Mendel's principle one gene controls one character but this is different way of expression. E.g., Marriage between two carriers of sickle cell will produce normal, carriers and sickle-cell anaemic children in 1 : 2 : 1 ratio. Sickle cell anaemics die leaving carriers and normals in ratio of 2 : 1.