Human skin colour is controlled by 3 genes A, B and C. Which of the following genotypes will have a skin colour different from the rest?

Options

A. AaBbCc
B. AAbbCc
C. aabBCC
D. AabbCc

Answer

To solve the question regarding human skin color controlled by three genes A, B, and C, we will analyze the genotypes provided in the options to determine which one will result in a skin color different from the rest.

### Step-by-Step Solution:

1. **Understanding Polygenic Inheritance**:
- Human skin color is a polygenic trait, meaning it is influenced by multiple genes. In this case, the genes involved are A, B, and C.
- Each gene can have a dominant (A, B, C) or recessive (a, b, c) allele. The dominant alleles contribute to higher melanin production, resulting in darker skin, while the recessive alleles lead to lower melanin production, resulting in lighter skin.

2. **Analyzing the Options**:
- We need to evaluate the number of dominant and recessive alleles in each genotype provided in the options.
- The more dominant alleles present, the darker the skin color will be, and the more recessive alleles present, the lighter the skin color will be.

3. **Counting Dominant and Recessive Alleles**:
- **Option 1**: AABBcc (2 dominant, 1 recessive)
- **Option 2**: AaBbCc (3 dominant, 0 recessive)
- **Option 3**: AAbbcc (2 dominant, 1 recessive)
- **Option 4**: aaBBcc (0 dominant, 3 recessive)

4. **Determining Skin Color**:
- Options 1, 2, and 3 have a combination of dominant alleles, indicating they will have darker skin tones.
- Option 4 has no dominant alleles (aaBBcc), which means it has the maximum number of recessive alleles, leading to very light skin color.

5. **Conclusion**:
- The genotype that will have a skin color different from the rest (which are darker) is **Option 4 (aaBBcc)**, as it results in the lightest skin color due to the absence of dominant alleles.

### Final Answer:
The genotype that will have a skin color different from the rest is **Option 4 (aaBBcc)**.