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Restriction Map Worksheet Generator

Two puzzles per sheet: a linear or circular molecule of 8 to 20 kilobases, cut by an abstract enzyme A, by an enzyme B and by both. The fragment sizes are listed in full and drawn as a schematic gel beside a size ladder. Pupils place the cut sites; the answer page draws the map. Every possible placement of the sites was searched to count how many different maps fit the three digests, and you can insist on puzzles with only one.

What this generator does

Gives restriction-mapping practice with a stated, checked answer: each puzzle says whether exactly one map fits, or how many do, so a pupil with a different but valid map is not marked wrong.

How to use this tool

  1. Choose a linear molecule, a circular (plasmid-like) one, or one of each.
  2. Leave 'Only puzzles with a single possible map' ticked for a puzzle with one right answer.
  3. Press Make two map puzzles, open the answers to check them, and print: puzzles and gels on page one, maps on page two.

Understanding the controls

Molecule
Linear, circular, or one of each. A circle with one A and one B site is never used, because any rotation would fit.
Single possible map
When ticked, only puzzles where the search found exactly one map are kept.
Paper and seed
Paper size and density for printing; a seed rebuilds the same pair while the generator is unchanged.

Worked examples

Linear, 10 kb
A gives 7 and 3 kb, B gives 7 and 3 kb, A + B gives 4, 3 and 3 kb. Only one map fits: A at 3 kb and B at 7 kb from one end.
Linear, 12 kb, two B sites
A: 8, 4. B: 7, 3, 2. A + B: 5, 3, 2, 2. Only one map fits: A at 4 kb, B at 2 and 9 kb.
Circular, 12 kb
A: 7, 5. B: 7, 5. A + B: 4, 3, 3, 2. Only one map fits: B at 2 and 9 kb, measured round from an A site, with the second A at 5 kb.

Common use cases

  • Practice for the double-digest questions in post-16 biology
  • Showing why a circle needs at least two cuts to give a puzzle
  • A logic starter: fragment sizes must add up to the whole molecule

How this generator works

Sites are placed at whole-kilobase positions and the three digests are computed by subtraction. A separate search then tries every placement of the same number of A and B sites, keeps those that give exactly the same three fragment lists, and counts them, treating a map read from the other end — and, for a circle, turned round — as the same map. Equal fragments are listed separately and drawn as one thicker band marked with the number of copies.

Randomness and fairness

Lengths and sites are drawn with the browser's cryptographically secure generator, or from one seeded draw when a seed is typed. Seeded sheets are deterministic, not cryptographic. The count of fitting maps is computed by exhaustive search, not estimated.

For how randomness is produced across the whole site, see how Generate Random works.

Limitations and good to know

  • The molecules and enzymes are invented. Sites sit on whole kilobases and every fragment is listed, which a real gel cannot promise: small fragments run off and close sizes merge.
  • The gel is schematic — band position falls with the logarithm of length — and is not a simulation of any real gel, stain or ladder.
  • One or two sites per enzyme only, which keeps the search exhaustive and the puzzles solvable by hand.

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