A set of genes will be in a complete linkage when the progeny phenotypes for parental (P) and recombinant (R) types are

Options

A. ` P = 0%, R = 100% `
B. `P = 50%, R = 50% `
C. ` P lt 50%, R gt 50%`
D. `P = 100%, R = 0%`

Answer

To determine when a set of genes is in complete linkage, we need to analyze the progeny phenotypes for parental (P) and recombinant (R) types. Here’s a step-by-step solution:

### Step-by-Step Solution:

1. **Understanding Complete Linkage**:
- Complete linkage occurs when two or more genes are located very close to each other on the same chromosome, such that they are inherited together without recombination.

2. **Analyzing Parental and Recombinant Types**:
- In a genetic cross, the offspring can exhibit two types of phenotypes: parental types (which resemble the parents) and recombinant types (which exhibit new combinations of traits).

3. **Identifying the Phenotype Ratios**:
- For genes that are completely linked, the expected ratio of offspring phenotypes will be:
- Parental types = 100%
- Recombinant types = 0%
- This means that all offspring will show the traits of the parental generation without any new combinations.

4. **Evaluating the Options**:
- Option 1: Parental = 0%, Recombinant = 100% (not possible, as some parental types must exist).
- Option 2: Parental = 50%, Recombinant = 50% (indicates independent assortment, not complete linkage).
- Option 3: Parental < 50%, Recombinant > 50% (impossible, as recombinants cannot exceed parental types in complete linkage).
- Option 4: Parental = 100%, Recombinant = 0% (this indicates complete linkage).

5. **Conclusion**:
- Therefore, a set of genes will be in complete linkage when the progeny phenotypes show 100% parental types and 0% recombinant types.

### Final Answer:
A set of genes will be in complete linkage when the progeny phenotypes for parental (P) types are 100% and recombinant (R) types are 0%.

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