Grade 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.What was new about Mendel's way of working, compared with others who had bred peas before him?
- a) He was the first to grow peas in a monastery garden
- b) He was the first to cross two different pea plants
- c) He used a microscope to look at the germ-cells
- d) He kept count of the individuals showing each trait in each generation
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.
3.Crossing a tall pea with a short one gave no plants of medium height. What did that tell Mendel?
- a) One parental trait was showing, rather than a mixture of the two
- b) Height is not an inherited trait in peas
- c) The two plants belonged to different species
- d) The short parent had contributed nothing to the offspring
4.Mendel counted 315 round yellow, 108 round green, 101 wrinkled yellow and 32 wrinkled green seeds. Which proportion is that closest to?
- a) 9 : 6 : 1
- b) 3 : 1 : 1 : 1
- c) 1 : 1 : 1 : 1
- d) 9 : 3 : 3 : 1
5.Why can a pea plant be tall with wrinkled seeds when neither of its grandparents was?
- a) The two traits sit on separate chromosomes and are inherited independently
- b) The two traits are controlled by the same gene
- c) New traits appear whenever a plant self-pollinates
- d) Wrinkled seeds turn a short plant tall
6.Sort each of Mendel's pea traits as the chapter classifies it.
Groups: Dominant · Recessive
- Short plants
- Wrinkled seeds
- Round seeds
- Tall plants
7.Snails can change sex during their lives. What does the chapter draw from that?
- a) In snails, sex is not genetically determined
- b) Temperature settles the sex of a snail
- c) Snails inherit sex from the mother alone
- d) Snails have no sex chromosomes
8.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) Neither — the temperature of development decides it
- d) Both equally, since each contributes one sex chromosome
Answer key — Grade 10 Science — Heredity
- 1. d) He kept count of the individuals showing each trait in each generation
- 2. 4 — The short plant
- 3. a) One parental trait was showing, rather than a mixture of the two
- 4. d) 9 : 3 : 3 : 1
- 5. a) The two traits sit on separate chromosomes and are inherited independently
- 6. Tall plants → Dominant; Round seeds → Dominant; Short plants → Recessive; Wrinkled seeds → Recessive
- 7. a) In snails, sex is not genetically determined
- 8. a) The father's, because the mother contributes an X either way