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Year 10 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.Which parent's contribution decides whether a human child is a boy or a girl?

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

  2. 2.How does a gene end up controlling how tall a plant grows?

    • a) It counts the number of cells the stem may have
    • b) It sets how efficient an enzyme is, which sets how much growth hormone is made
    • c) It decides how much water the roots take up
    • d) It stretches the cells of the stem directly

  3. 3.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

  4. 4.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

  5. 5.A trait that shows itself in a pea plant when both copies of the factor are of that kind, and not otherwise — what is such a trait called? Answer with one word.

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

    Groups: Dominant · Recessive

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

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

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

  8. 8.What was new about Mendel's way of working, compared with others who had bred peas before him?

    • a) He was the first to cross two different pea plants
    • b) He kept count of the individuals showing each trait in each generation
    • c) He used a microscope to look at the germ-cells
    • d) He was the first to grow peas in a monastery garden

Answer key — Year 10 Science — Heredity

  1. 1. b) The father's, because the mother contributes an X either way
  2. 2. b) It sets how efficient an enzyme is, which sets how much growth hormone is made
  3. 3. c) One parental trait was showing, rather than a mixture of the two
  4. 4. 4 — The short plant
  5. 5. recessive
  6. 6. Tall plants → Dominant; Round seeds → Dominant; Short plants → Recessive; Wrinkled seeds → Recessive
  7. 7. c) The temperature at which the fertilised eggs are kept
  8. 8. b) He kept count of the individuals showing each trait in each generation