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Mendel's monohybrid cross: dominant and recessive traits sheet
5-mark answer frame

Explain Mendel's monohybrid cross using pure tall and pure short pea plants. What do the results show?

How to lay out the answer. Follow the frame, then write it in your own words.

  1. 1 · Define in one line. A monohybrid cross follows the inheritance of one pair of contrasting traits.
  2. 2 · Parents and F1. TT (tall) × tt (short) → all Tt, all tall.
  3. 3 · Self-pollinate F1. Tt × Tt; each parent gives gametes T and t.
  4. 4 · Draw the checkerboard. [Checkerboard: T, t × T, t → TT, Tt, Tt, tt]
  5. 5 · Write the ratios. 3 tall : 1 short (phenotype); 1 TT : 2 Tt : 1 tt (genotype).
  6. 6 · Conclusions.
    • Each trait is controlled by two copies, one from each parent.
    • Tall is dominant; short is recessive.
    • The recessive trait is hidden in F1 but not lost.
  7. 7 · Link to daily life. Plant breeders use these rules to develop new crop varieties.
  8. 8 · Close in one line. So traits are passed on as separate units that keep their identity.

Scoring tip: Write Parents, Gametes, F1 and F2 as labelled lines, and box both ratios.