In a mendel's monohybrid cross for the shapes of pea seeds,1600 seeds were obtained in F_2 generation. What will be the number of round seed and hybrid round seed, respectively?

Options

A. 1200 & 800
B. 800 & 1200
C. 400 & 800
D. 1200 & 400

Answer

To solve the problem regarding Mendel's monohybrid cross for the shapes of pea seeds, we need to understand the inheritance pattern and the resulting phenotypic ratios in the F2 generation.

### Step-by-Step Solution:

1. **Understanding the Cross**: In Mendel's monohybrid cross, we are dealing with two traits: round seeds (dominant) and wrinkled seeds (recessive). The round seed genotype is represented as "R" (dominant), and the wrinkled seed genotype is represented as "r" (recessive).

2. **F1 Generation**: When we cross two pure lines (RR x rr), all offspring in the F1 generation will be heterozygous (Rr) and exhibit the dominant phenotype, which is round seeds.

3. **F2 Generation**: When the F1 generation (Rr) is self-fertilized, the resulting F2 generation will show a phenotypic ratio of 3:1 for dominant to recessive traits. This means:
- 3 parts will be round seeds (RR or Rr)
- 1 part will be wrinkled seeds (rr)

4. **Genotypic Ratio**: The genotypic ratio in the F2 generation will be 1:2:1, which corresponds to:
- 1 RR (homozygous round)
- 2 Rr (heterozygous round)
- 1 rr (homozygous wrinkled)

5. **Calculating Total Seeds**: We are given that there are 1600 seeds in the F2 generation.

6. **Calculating Round Seeds**:
- The total round seeds (RR + Rr) = 3 parts out of 4.
- Therefore, the number of round seeds = (3/4) * 1600 = 1200 seeds.

7. **Calculating Hybrid Round Seeds**:
- The hybrid round seeds (Rr) = 2 parts out of 4.
- Therefore, the number of hybrid round seeds = (2/4) * 1600 = 800 seeds.

8. **Final Answer**: Thus, the number of round seeds is 1200, and the number of hybrid round seeds is 800.

### Summary:
- Number of round seeds = 1200
- Number of hybrid round seeds = 800