In Mendel's experiments with garden pea, round seed shape (RR) was dominant over wrinkled seeds (rr), yellow cotyledon (YY) was dominant over green cotyledon (yy). What are the expected phenotypes in the `F_(2)`-generation of the cross RRYY `xx` rryy ?

Options

A. Only round seeds with green cotyledons
B. Only wrinkled seeds with yellow cotyledons
C. Only wrinkled seeds with yellow cotyledons
D. Round seeds with yellow cotyledons and wrinkled seeds with yellow cotyledons

Explanation

To solve the question regarding the expected phenotypes in the F2 generation of the cross between RRYY and rryy, we will follow these steps:

### Step-by-Step Solution:

1. **Identify the Parental Genotypes**:
- The parental plants are RRYY (homozygous dominant for both traits: round seeds and yellow cotyledons) and rryy (homozygous recessive for both traits: wrinkled seeds and green cotyledons).

2. **Determine the Gametes Produced by Each Parent**:
- The RRYY parent can only produce one type of gamete: RY.
- The rryy parent can only produce one type of gamete: ry.

3. **Perform the F1 Cross**:
- When we cross RRYY (RY) with rryy (ry), all offspring in the F1 generation will be RrYy (heterozygous for both traits). This means they will all have round seeds and yellow cotyledons because both traits are dominant.

4. **Selfing the F1 Generation**:
- To find the F2 generation, we need to self-cross the F1 individuals (RrYy x RrYy).

5. **Determine the Possible Gametes from F1**:
- Each F1 plant (RrYy) can produce four types of gametes: RY, Ry, rY, and ry.

6. **Construct a Punnett Square**:
- Set up a 4x4 Punnett square to determine the genotypes of the F2 generation by crossing the gametes:
```
RY Ry rY ry
---------------------
RY | RRYY RRYy RrYY RrYy
---------------------
Ry | RRYy RRyy RrYy Rryy
---------------------
rY | RrYY RrYy rrYY rrYy
---------------------
ry | RrYy Rryy rrYy rryy
```

7. **Count the Phenotypes**:
- From the Punnett square, we can categorize the phenotypes:
- Round seeds with yellow cotyledons (RRYY, RRYy, RrYY, RrYy): 9
- Round seeds with green cotyledons (RRyy, Rryy): 3
- Wrinkled seeds with yellow cotyledons (rrYY, rrYy): 3
- Wrinkled seeds with green cotyledons (rryy): 1

8. **Determine the Phenotypic Ratio**:
- The phenotypic ratio is 9 (round yellow) : 3 (round green) : 3 (wrinkled yellow) : 1 (wrinkled green).

9. **Identify the Expected Phenotypes**:
- The expected phenotypes in the F2 generation are:
- Round seeds with yellow cotyledons
- Round seeds with green cotyledons
- Wrinkled seeds with yellow cotyledons
- Wrinkled seeds with green cotyledons

### Conclusion:
The expected phenotypes in the F2 generation from the cross RRYY x rryy are:
- Round seeds with yellow cotyledons
- Round seeds with green cotyledons
- Wrinkled seeds with yellow cotyledons
- Wrinkled seeds with green cotyledons