Two genes, C and D, are located on the same chromosome. In a testcross, the recombinant frequency observed between them is 20%. If the observed double‑crossover frequency is 2% while the expected double‑crossover frequency (based on independent recombination of two intervals each 20%) is 4%, what is the coefficient of coincidence and the interference?
Answer
Coefficient of coincidence = 0.5, Interference = 0.5
The correct answer is Coefficient of coincidence = 0.5, Interference = 0.5 — Thus the correct answer is "Coefficient of coincidence = 0.5, Interference = 0.5".
Step-by-step solution
- Calculate expected double‑crossover frequency: expected = (recombination frequency of first interval) × (recombination frequency of second interval) = 0.20 × 0.20 = 0.04 (4%).
- Observed double‑crossover frequency is given as 2% = 0.02.
- Compute coefficient of coincidence (c) = observed / expected = 0.02 / 0.04 = 0.5.
- Interference (I) = 1 − c = 1 − 0.5 = 0.5.
- Select the option that matches c = 0.5 and I = 0.5, which is option a.
- Thus the correct answer is "Coefficient of coincidence = 0.5, Interference = 0.5".
Common mistake: Dividing observed double crossovers by the single‑interval recombination frequency instead of by the product of the two intervals.
Concept tested: Linkage mapping – coefficient of coincidence & interference
Published · How this solution was prepared and checked
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