A field of pea has plants bearing both yellow and green seeds green sheet colour is preferred, which of the following cross if performed repatedly has a higher probability for obtaining pure line for green seed colour?

Options

A. `YY × YY`
B. `Yy × YY`
C. `Yy × yy`
D. `Yy × Yy`

Answer

To solve the question about obtaining a pure line for green seed color in pea plants, we can follow these steps:

### Step 1: Understand the Genetics
Pea plants can have either yellow seeds or green seeds. Yellow seed color is dominant (Y), while green seed color is recessive (y). This means that:
- YY = Yellow seeds (homozygous dominant)
- Yy = Yellow seeds (heterozygous)
- yy = Green seeds (homozygous recessive)

### Step 2: Identify the Goal
We want to obtain a pure line for green seed color (yy). This means we need to ensure that both alleles are recessive.

### Step 3: Analyze Possible Crosses
We need to consider the crosses that can produce the recessive phenotype (green seeds):
1. YY x YY → All offspring will be YY (yellow)
2. YY x Yy → 50% YY (yellow), 50% Yy (yellow)
3. Yy x Yy → 25% YY (yellow), 50% Yy (yellow), 25% yy (green)
4. yy x yy → All offspring will be yy (green)

### Step 4: Determine the Best Cross
To maximize the chances of obtaining pure green seeds (yy), the best cross would be:
- **Yy x Yy**: This cross gives a 25% chance of producing yy (green seeds).

### Step 5: Conclusion
The cross that has the highest probability of obtaining a pure line for green seed color is **Yy x Yy**.

### Summary of the Solution
The best cross to obtain a pure line for green seed color is Yy x Yy, which provides a 25% chance of producing pure green seeds (yy).