● Science 8 · Term 1 · Week 4

Ten Minutes at Home: The Coin That Does Not Remember

Nothing to buy. Ten minutes with two coins. Your child is learning to read a Punnett square, which is easy — and to understand what it means, which is not, and which a great many adults get wrong too. This activity is about the hard half.

The activity: four flips, four children

minutes: 10 Materials: two coins of any value.

  1. Explain the rule: heads means one version of a gene, tails means the other. Two tails together is the version you can see.
  2. Ask: <q>If we flip both coins four times, how many times will we get two tails?</q>
  3. Whatever they say, write it down. Then flip four times and record the results.
  4. It will usually not be one. Ask: <q>Did we do something wrong?</q>
  5. Now flip four times again. And again. Keep a tally of every set of four.
  6. Ask: <q>Is the coin keeping track of what happened before?</q>
  7. Finish with: <q>So each flip is a fresh chance. Does that change what one in four means?</q>

Three things to avoid

What usually happensInstead
Saying <q>it's due</q> or <q>we're owed one now</q>.This is the exact belief the lesson is trying to remove. A coin has no memory, and neither does inheritance. Every child of the same parents starts from the same odds.
Saying a trait <q>skipped a generation</q> as if the trait went somewhere.It did not go anywhere. It was carried, unseen, by a parent who had one copy of it. Your child is learning why that is possible, and the word to use is <em>carried</em>.
Treating a surprising result as a mistake.Four out of four is unusual and entirely possible — about a one in 256 chance. Unlikely is not the same as wrong, and telling the two apart is most of what this topic is.

Three signs it is working

If you only do one part, do step 6 — <b>is the coin keeping track?</b> Everything else in this topic follows from the answer being no, and it is the piece that most often never lands.