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Genetic Linkage and Recombination Mapper

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About This MicroSim

This tool lets students calculate recombination frequencies (RF) from test cross offspring data and construct a genetic linkage map. Three gene pairs are entered, RF is auto-calculated, gene order is determined (the largest RF identifies the outside genes), and genes are positioned proportionally on a chromosome bar.

How to Use

  1. Load an example using the dropdown and "Load Example" button (Drosophila or Corn).
  2. The data panel shows recombinant counts, total offspring, and calculated RF for each gene pair.
  3. The map distances panel shows the determined gene order and centiMorgan (cM) distances.
  4. The chromosome map at the bottom positions genes proportionally with distance labels.
  5. A consistency check verifies whether the sum of segments matches the largest RF.

Lesson Plan

Grade Level

9-12 (college placement Biology)

Duration

10-15 minutes

Prerequisites

  • Understanding of linked genes and crossing over
  • Knowledge that recombination frequency reflects physical distance between genes
  • Ability to calculate RF = (recombinants / total) x 100

Activities

  1. Exploration (5 min): Load the Drosophila example. Observe how the three RFs determine gene order and map distances. Note the consistency check result.
  2. Guided Practice (5 min): Using the map, answer: "Which two genes are farthest apart? How do you know?" Explain why the largest RF identifies the outside genes.
  3. Assessment (5 min): Load the Corn example and predict the gene order before looking at the map. Verify your prediction.

Assessment

  • Can students calculate RF from offspring data?
  • Can students determine gene order from three pairwise RFs?
  • Can students explain why double crossovers can make the sum of segments differ from the largest RF?

References

  1. Genetic linkage - Wikipedia
  2. Recombination frequency - Wikipedia
  3. Centimorgan - Wikipedia