Question

Explain codominance in colour coat in cattle with checker board method.

Answer 1

1. Coat colour in cattle is a classic example of co-dominance.
2. There are two types, one with a red coat (skin with red colour hair) and the other with a white coat (with white hair).
3. When red cattle (RR) is crossed with white cattle (WW), F1 hybrids (RW) have roan colour. Roans have a mixture of red and white colour hair.
4. Thus, both traits are expressed equally. In F2 generation (produced by interbreeding of roans), red (RR), roans (RW) and white (WW) are produced in the ratio 1: 2: 1.

Phenotypic ratio → 1 : 2 : 1 (1 Red coat : 2 Roan : 1 White coat)

Genotypic ratio → 1 : 2 : 1 (1 RR : 2 RW : 1 WW)