How many genes are responsible for?
(i)ABO system of blood group (ii)Skin colour in human

Explanation

To answer the question regarding how many genes are responsible for the ABO blood group system and skin color in humans, we can break it down as follows:

### Step-by-Step Solution:

1. **Understanding ABO Blood Group System**:
- The ABO blood group system is determined by a single gene known as the **I gene**.
- This gene has three alleles: **IA**, **IB**, and **i**.
- The IA and IB alleles are co-dominant, meaning that if both are present, they will express themselves equally, resulting in the AB blood group.
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