Heterozygous tall and red flowered pea plants are selfed and total 2000 seeds are collected . What is the total number of seeds for both heterozygous traits ?

Options

A. 250
B. 500
C. 1250
D. 750

Answer

To solve the problem of determining the total number of seeds that are heterozygous for both traits (tall and red flowered) from the selfing of heterozygous pea plants, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Genotype of the Parent Plants:**
The parent plants are heterozygous for both traits. This means their genotype can be represented as TtRr, where:
- T = tall (dominant)
- t = short (recessive)
- R = red flower (dominant)
- r = white flower (recessive)

2. **Determine the Gametes Produced:**
When these heterozygous plants are selfed (crossed with themselves), they can produce four types of gametes:
- TR (tall and red)
- Tr (tall and white)
- tR (short and red)
- tr (short and white)

3. **Create a Punnett Square:**
To find the offspring genotypes, we can set up a Punnett square using the gametes from both parents:
```
TR Tr tR tr
---------------------------
TR | TTRR TTRr TtRR TtRr
---------------------------
Tr | TTRr TTrr TtRr Ttrr
---------------------------
tR | TtRR TtRr ttRR ttRr
---------------------------
tr | TtRr Ttrr ttRr ttrr
```

4. **Count the Offspring Genotypes:**
From the Punnett square, we can count the genotypes:
- TTRR: 1
- TTRr: 2
- TtRR: 2
- TtRr: 4 (heterozygous for both traits)
- TTrr: 1
- Ttrr: 2
- ttRR: 1
- ttRr: 2
- ttrr: 1

Total offspring = 16 (1 + 2 + 2 + 4 + 1 + 2 + 1 + 2 + 1 = 16)

5. **Identify Heterozygous Offspring:**
The heterozygous combinations for both traits (TtRr) appear 4 times in the offspring.

6. **Calculate the Proportion of Heterozygous Offspring:**
The proportion of heterozygous offspring for both traits is:
\[ \text{Proportion of heterozygous} = \frac{4}{16} = \frac{1}{4} \]

7. **Calculate the Total Number of Heterozygous Seeds:**
Given that a total of 2000 seeds were collected, the number of seeds that are heterozygous for both traits is:
\[ \text{Number of heterozygous seeds} = \frac{1}{4} \times 2000 = 500 \]

### Final Answer:
The total number of seeds that are heterozygous for both traits (tall and red flowered) is **500**.

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