- Place B and C at the ends, 45 map units apart.
- Place A 30 map units from C, so A is 15 map units from B (since 45 - 30 = 15).
- Place D 25 map units from A. Since A is 15 map units from B, D must be 10 map units beyond A toward C (15 + 10 = 25 from A), making D 25 map units from B and 20 map units from C.
- Verify B-D is 40 map units: B to A is 15, A to D is 10, total 25 — this contradicts the given 40%. Adjust: if B to D is 40, and B to A is 15, then A to D must be 25, placing D 25 map units from A away from B, which puts D 20 map units from C (45 - 25 = 20). But given A-D is 25%, which matches, and B-D is 40% — 15 + 25 = 40, correct. Also, D to C should be 20%, but not given; however, the distances are consistent with the provided crossover frequencies.
- Final order: B —15— A —25— D —20— C, with total B to C = 45 map units.
Parent Tip: Review the logic above to help your child master the concept of chromosome mapping worksheet.
