Half the set, four ways

Science · Genetics & Evolution · ages 14-16

Name ______________________ Date ____________

How does a gamete's chromosome number compare with a body cell?
- Half
- Double
- Equal
In the sperm-making model shown in class, how many cells does meiosis make?
- Two
- Four
- One
Fertilisation restores the full double set of chromosomes.
Circle one: True False
What makes the four cells genetically different from each other?
- Extra rounds of copying
- Swaps and random line-up
- Fertilisation before division
What would happen to chromosome sets without halving?
- Sets would stay the same
- Sets would vanish
- They would double
In our body-cell model, how does mitosis differ from meiosis?
- Two divisions, four different haploid cells
- No division, one resting cell
- One division, two identical diploid cells
Sexual reproduction feeds evolution because meiosis deals new gene combinations each generation.
Circle one: True False
A pupil says clones vary because mitosis shuffles genes. What is wrong?
- Mitosis makes four cells
- Copies without shuffling
- Clones come from fertilisation

Answer key

For grown-ups. Fold this page away before handing over the rest.

Half · Gametes are haploid with one set, while body cells are diploid with two.
Four · One doubling plus two divisions gives four haploid products in the model. Human egg-making keeps one working egg.
True · Two haploid halves meet and rebuild the diploid set.
Swaps and random line-up · Partners swap segments and line up at random, so matching gametes are unlikely.
They would double · Two sets plus two sets makes four, then eight, doubling each generation.
One division, two identical diploid cells · Mitosis keeps the starting set number. In the body-cell model that means one division into two identical diploid cells.
True · Shuffled gametes can deal a new hand every generation, feeding variety and selection.
Copies without shuffling · Mitosis copies without shuffling, so clones stay identical. Shuffling belongs to meiosis.