A heterozygous pea plant producing intermediate strach grain size is selfed. What number of progeny will produce large strach grain size out of 4000 pea plants obtained ?

Options

A. 3000
B. 2000
C. 1000
D. 500

Answer

To solve the problem of determining how many progeny will produce large starch grain size out of 4000 pea plants obtained from selfing a heterozygous pea plant, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Genotypes**:
- We denote the allele for large starch grain size as **G** (dominant) and the allele for small starch grain size as **g** (recessive).
- The heterozygous pea plant has the genotype **Gg**, which produces an intermediate starch grain size.

2. **Self-Cross the Heterozygous Plant**:
- When we self the heterozygous plant (Gg x Gg), we need to determine the possible gametes produced by each parent.
- Each parent can produce two types of gametes: **G** and **g**.

3. **Construct a Punnett Square**:
- We set up a Punnett square to visualize the offspring from the self-cross:
```
G g
----------------
G | GG | Gg |
----------------
g | Gg | gg |
----------------
```
- The resulting genotypes from this cross are:
- **GG** (homozygous dominant)
- **Gg** (heterozygous)
- **Gg** (heterozygous)
- **gg** (homozygous recessive)

4. **Determine the Phenotypic Ratio**:
- From the Punnett square, we can see the phenotypes:
- **Large starch grain size (GG or Gg)**: 3 (GG, Gg, Gg)
- **Small starch grain size (gg)**: 1
- This gives us a phenotypic ratio of **3:1** for large to small starch grain sizes.

5. **Calculate the Number of Progeny with Large Starch Grain Size**:
- Out of 4000 total progeny, we need to find the number that will produce large starch grain size.
- Using the ratio, we calculate:
\[ \text{Number of large starch grain size} = \frac{3}{4} \times 4000 = 3000 \]

### Final Answer:
Thus, the number of progeny that will produce large starch grain size out of 4000 pea plants is **3000**.

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