To solve the problem of finding the recombinant phenotypic ratio in the F2 generation from the parental cross TTRR x ttrr, we can follow these steps:
### Step-by-Step Solution:
1. **Identify Parent Genotypes and Traits:**
- The parental genotypes are TTRR (tall, round seeds) and ttrr (dwarf, wrinkled seeds).
- T (tall) is dominant over t (dwarf), and R (round) is dominant over r (wrinkled).
2. **Determine Gametes from Parents:**
- The gametes produced by TTRR will be TR.
- The gametes produced by ttrr will be tr.
- Therefore, the F1 generation will consist of all offspring having the genotype TtRr (tall, round seeds).
3. **Selfing the F1 Generation:**
- When we self the F1 generation (TtRr x TtRr), we can use a Punnett square to determine the F2 generation.
4. **Constructing a Punnett Square:**
- The gametes from TtRr will be TR, Tr, tR, and tr.
- Setting up the Punnett square will give us a 4x4 grid.
5. **Filling in the Punnett Square:**
- The resulting genotypes from the Punnett square will be:
- TTRR (Tall, Round)
- TTRr (Tall, Round)
- TtRR (Tall, Round)
- TtRr (Tall, Round)
- TtRr (Tall, Round)
- Ttrr (Tall, Wrinkled)
- ttRR (Dwarf, Round)
- ttRr (Dwarf, Round)
- ttrr (Dwarf, Wrinkled)
6. **Counting Phenotypes:**
- The phenotypic ratio can be summarized as follows:
- Tall Round (T_R): 9 (TTRR, TTRr, TtRR, TtRr)
- Tall Wrinkled (T_rr): 3 (Ttrr)
- Dwarf Round (ttR_): 3 (ttRR, ttRr)
- Dwarf Wrinkled (ttrr): 1 (ttrr)
7. **Identifying Recombinant Phenotypes:**
- The recombinant phenotypes are those that differ from the parents:
- Tall Wrinkled (T_rr) and Dwarf Round (ttR_).
- Thus, the recombinant phenotypes are 3 (Tall Wrinkled) + 3 (Dwarf Round) = 6.
8. **Calculating the Recombinant Phenotypic Ratio:**
- The total number of phenotypes in F2 is 16 (9 + 3 + 3 + 1).
- The recombinant phenotypic ratio is therefore 6 out of 16, which simplifies to 3:3 or 1:1.
### Final Answer:
The recombinant phenotypic ratio in F2 generation is **3:3**.
