Linkage ratio of 7 : 1 :1: 7 in case of dihybrid test cross means that there are

Options

A. 2 parental and 14 recombinant plants
B. 14 parental and 2 recombinantplants
C. 9 parental and 7 recombinant plants
D. 8 parental and 8 recombinant plants

Answer

To solve the question regarding the linkage ratio of 7:1:1:7 in the case of a dihybrid test cross, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Test Cross**:
- A dihybrid test cross involves two traits, where an F1 individual (heterozygous for both traits) is crossed with a double recessive individual (homozygous recessive for both traits).

2. **Identifying the Linkage Ratio**:
- The given linkage ratio is 7:1:1:7. This indicates the distribution of offspring phenotypes in the F2 generation resulting from the test cross.

3. **Determining Parental and Recombinant Types**:
- In a dihybrid test cross, the parental types (those that resemble the parents) will be more frequent than the recombinant types (those that show combinations of traits not found in the parents).
- In this case, the parental phenotypes correspond to the 7s in the ratio, while the recombinant phenotypes correspond to the 1s.

4. **Calculating the Number of Offspring**:
- The total ratio parts are 7 + 1 + 1 + 7 = 16.
- This means that out of 16 offspring, 14 are parental types (7 + 7) and 2 are recombinant types (1 + 1).

5. **Conclusion**:
- Therefore, in the F2 generation, there are 14 parental types and 2 recombinant types.

### Final Answer:
The linkage ratio of 7:1:1:7 in a dihybrid test cross means that there are 14 parental types and 2 recombinant types.

---