How many types & in what ratio the gametes are produced by a dihybrid heterozygous :-

Options

A. 4 types in the ratio of `9:3:3:1`
B. 2 types in the ratio of `3:1`
C. 3 types in the ratio of `1:2:1`
D. 4 types in the ratio of `1:1:1:1`

Answer

To solve the question of how many types of gametes are produced by a dihybrid heterozygous organism and in what ratio, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Dihybrid Cross**:
A dihybrid cross involves two traits, each represented by two alleles. For example, consider the traits for seed color (Yellow - Y, Green - y) and seed shape (Round - R, Wrinkled - r).

2. **Genotype of Dihybrid Heterozygous**:
A dihybrid heterozygous organism will have the genotype YyRr, where Yy represents the seed color alleles and Rr represents the seed shape alleles.

3. **Determining Gametes**:
To find the types of gametes produced, we can use the principle of independent assortment. Each allele can combine with each of the other alleles. The possible combinations of alleles in the gametes can be determined as follows:
- From Yy, the possible alleles are Y and y.
- From Rr, the possible alleles are R and r.
- The combinations of these alleles will be:
- YR (Yellow and Round)
- Yr (Yellow and Wrinkled)
- yR (Green and Round)
- yr (Green and Wrinkled)

4. **Counting the Types of Gametes**:
We have identified four different combinations of gametes: YR, Yr, yR, and yr. Therefore, the number of types of gametes produced is 4.

5. **Determining the Ratio**:
When we consider the self-fertilization of the F1 generation (YyRr x YyRr), the resulting phenotypic ratio of the offspring will be 9:3:3:1. However, the ratio of the gametes produced is not expressed in this way. The ratio of the gametes produced is 1:1:1:1, as each type of gamete is produced equally.

### Final Answer:
The dihybrid heterozygous produces **4 types of gametes** in the ratio of **1:1:1:1**.

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