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Year 11 Science — Heredity

Work out the ratios of a Mendelian cross, tell a dominant trait from a recessive one, and explain how chromosomes let two traits be inherited independently and how they settle a child's sex.

Name: ________________________

  1. 1.Put the stages of Mendel's one-character experiment in order, starting with "Cross a tall pea plant with a short one".

    • Cross a tall pea plant with a short one
    • Let those first-generation plants self-pollinate
    • The whole of the first generation comes out tall
    • One quarter of the second generation comes out short

  2. 2.Four second-generation pea plants are drawn to scale below. Tap the one that must have inherited two copies of the recessive factor.

    Write the number of the part.

    1234

  3. 3.Which parent's contribution decides whether a human child is a boy or a girl?

    • a) The father's, because the mother contributes an X either way
    • b) The mother's, because she carries two X chromosomes
    • c) Both equally, since each contributes one sex chromosome
    • d) Neither — the temperature of development decides it

  4. 4.Mendel counted 315 round yellow, 108 round green, 101 wrinkled yellow and 32 wrinkled green seeds. Which proportion is that closest to?

    • a) 1 : 1 : 1 : 1
    • b) 9 : 6 : 1
    • c) 3 : 1 : 1 : 1
    • d) 9 : 3 : 3 : 1

  5. 5.In some reptiles, what decides whether the animals developing in the eggs will be male or female?

    • a) The size of the egg
    • b) The temperature at which the fertilised eggs are kept
    • c) The sex chromosomes inherited from the father
    • d) The order in which the eggs were laid

  6. 6.Sort each of Mendel's pea traits as the chapter classifies it.

    Groups: Dominant · Recessive

    • Tall plants
    • Wrinkled seeds
    • Short plants
    • Round seeds

  7. 7.Match each description to the term for it.

    • A section of DNA holding the information for one protein
    • One of the separate pieces a gene set is divided into
    • A chromosome
    • A gene

  8. 8.Crossing a tall pea with a short one gave no plants of medium height. What did that tell Mendel?

    • a) Height is not an inherited trait in peas
    • b) The short parent had contributed nothing to the offspring
    • c) One parental trait was showing, rather than a mixture of the two
    • d) The two plants belonged to different species

Answer key — Year 11 Science — Heredity

  1. 1. 1. Cross a tall pea plant with a short one 2. The whole of the first generation comes out tall 3. Let those first-generation plants self-pollinate 4. One quarter of the second generation comes out short
  2. 2. 4 — The short plant
  3. 3. a) The father's, because the mother contributes an X either way
  4. 4. d) 9 : 3 : 3 : 1
  5. 5. b) The temperature at which the fertilised eggs are kept
  6. 6. Tall plants → Dominant; Round seeds → Dominant; Short plants → Recessive; Wrinkled seeds → Recessive
  7. 7. A section of DNA holding the information for one protein → A gene; One of the separate pieces a gene set is divided into → A chromosome
  8. 8. c) One parental trait was showing, rather than a mixture of the two