You began as one single cell with half its instructions from each parent. Here's how the numbers work out.
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Students will explain that sex cells are haploid (23 chromosomes in humans) while body cells are diploid (46), describe meiosis as two divisions that produce four sex cells, and explain that fertilization joins an egg and a sperm into a diploid zygote.
Mitosis keeps the chromosome number the same. Meiosis halves it. That difference is the whole lesson.
The book's numbers question is the best hook: if a sex cell had 46 chromosomes, a new person would have 92, and the number would double every generation.
Use pairs of socks as chromosome pairs. A body cell holds all the pairs; a sex cell gets one sock from each pair. Put two sex cells together and every pair is whole again.
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Before You Start
The words this lesson uses. Tap a card to see what it means, then come back to them whenever a question uses one.
Part One
Questions about the story you just read. Pick your answer straight off, or press Find it in the story if you would rather hunt for the sentence first.
Part Two
The word cards are at the top of this page. Look back at them as often as you need, then answer.