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

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

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

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

  3. 3.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 sex chromosomes inherited from the father
    • c) The order in which the eggs were laid
    • d) The temperature at which the fertilised eggs are kept

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

    Groups: Dominant · Recessive

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

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

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

  7. 7.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
    • One quarter of the second generation comes out short
    • Let those first-generation plants self-pollinate
    • The whole of the first generation comes out tall

  8. 8.The short plants reappear in the second generation, after a first generation that was tall throughout. What does that show?

    • a) The short trait was created afresh in the second generation
    • b) Both traits were inherited by the first generation, with one of them expressed
    • c) Self-pollination changed the tall factor into a short one
    • d) The first generation was not really tall

Answer key — Class 10 Science — Heredity

  1. 1. c) It sets how efficient an enzyme is, which sets how much growth hormone is made
  2. 2. a) He kept count of the individuals showing each trait in each generation
  3. 3. d) The temperature at which the fertilised eggs are kept
  4. 4. 4 — The short plant
  5. 5. Tall plants → Dominant; Round seeds → Dominant; Short plants → Recessive; Wrinkled seeds → Recessive
  6. 6. a) 9 : 3 : 3 : 1
  7. 7. 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
  8. 8. b) Both traits were inherited by the first generation, with one of them expressed