A plant has genotype TtRrGgPP. On selfing of this plant, what is the sum total of phenotypic categories ?

Options

A. 8
B. 16
C. 4
D. 27

Answer

To solve the question regarding the sum total of phenotypic categories from the genotype TtRrGgPP, we will follow these steps:

### Step 1: Identify the alleles in the genotype
The given genotype is TtRrGgPP. Here, we can break it down into the following alleles:
- Tt: 2 alleles (T and t)
- Rr: 2 alleles (R and r)
- Gg: 2 alleles (G and g)
- PP: 1 allele (P, since it is homozygous)

### Step 2: Determine the number of different gametes produced
To find the number of different gametes that can be produced, we consider the combinations of alleles from each gene:
- For Tt, there are 2 possibilities: T or t.
- For Rr, there are 2 possibilities: R or r.
- For Gg, there are 2 possibilities: G or g.
- For PP, there is only 1 possibility: P.

The total number of gametes can be calculated by multiplying the number of possibilities for each gene:
\[ \text{Total gametes} = 2 (from Tt) \times 2 (from Rr) \times 2 (from Gg) \times 1 (from PP) = 2 \times 2 \times 2 \times 1 = 8 \]

### Step 3: Determine the phenotypic categories from the gametes
When selfing the plant, we will perform a dihybrid cross with the gametes produced. The phenotypic ratio for a dihybrid cross (considering two traits) typically follows the 9:3:3:1 ratio. However, since we have three traits (T, R, G) and one trait is homozygous (P), we will have to consider the combinations of the three heterozygous traits.

The total phenotypic categories can be calculated as follows:
- For Tt: 2 phenotypes (Tall and short)
- For Rr: 2 phenotypes (Round and wrinkled)
- For Gg: 2 phenotypes (Green and yellow)
- For PP: 1 phenotype (since it is homozygous)

The total number of phenotypic categories is:
\[ \text{Total phenotypes} = 2 (from Tt) \times 2 (from Rr) \times 2 (from Gg) \times 1 (from PP) = 2 \times 2 \times 2 \times 1 = 8 \]

### Step 4: Conclusion
Thus, the sum total of phenotypic categories when the plant with genotype TtRrGgPP is selfed is 8.

### Final Answer
The sum total of phenotypic categories is **8**.

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