Maximum height of a plant is 30 ft. And minimum height is 10 ft. If plant height is controlled by 3 pairs of genes, then the height of plant with genotype AaBbCc will be -

Options

A. 13.2 ft.
B. 23.2 ft.
C. 16.6 ft.
D. 19.9 ft.

Answer

To solve the problem of determining the height of a plant with the genotype AaBbCc, given that the maximum height is 30 ft and the minimum height is 10 ft, and that plant height is controlled by three pairs of genes, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Maximum and Minimum Heights**:
- Maximum height of the plant = 30 ft
- Minimum height of the plant = 10 ft

2. **Calculate the Range of Height**:
- Height range = Maximum height - Minimum height
- Height range = 30 ft - 10 ft = 20 ft

3. **Determine the Number of Polygenes**:
- The problem states that plant height is controlled by 3 pairs of genes.
- Each pair of genes contributes to the height, so the total number of alleles (polygene) = 3 pairs × 2 alleles per pair = 6 alleles.

4. **Calculate the Contribution of Each Gene**:
- Contribution of each gene = Height range / Number of polygenes
- Contribution of each gene = 20 ft / 6 = 3.33 ft (approximately)

5. **Determine the Contribution of Dominant Genes**:
- In the genotype AaBbCc, each gene is heterozygous, meaning there are 3 dominant alleles contributing to the height.
- Total contribution from dominant genes = Contribution of each gene × Number of dominant genes
- Total contribution from dominant genes = 3.33 ft × 3 = 9.99 ft (approximately 10 ft)

6. **Calculate the Total Height of the Plant**:
- The total height of the plant = Minimum height + Contribution from dominant genes
- Total height = 10 ft + 9.99 ft = 19.99 ft

7. **Round to Appropriate Decimal Places**:
- Rounding 19.99 ft gives us approximately 19.9 ft.

### Final Answer:
The height of the plant with genotype AaBbCc will be **19.9 ft**.