Teacher sheet · Ages 10–11 · about 45–50 minutes
Genes, chromosomes and inheritance
Lesson page: echoesof.science/school/dna/ages-10-11/ · Pupil worksheet: echoesof.science/school/dna/ages-10-11/print/
Learning aims
- Describe where DNA is kept and how genes, chromosomes and DNA are related.
- Know that humans have 23 pairs of chromosomes, one of each pair from each parent.
- Apply base pairing and explain how DNA is copied.
- Model inheritance with chance and compare small and large samples.
Lesson plan
| Time | Activity |
|---|---|
| 5 min | Starter: a library (nucleus), books (chromosomes), recipes (genes), letters (bases). |
| 10 min | Read the text; write a strand and its partner on the board. |
| 20 min | Coin-toss babies, then pool class results. |
| 5 min | Game: DNA, gene or chromosome? |
| 5 min | Quiz; worksheet. |
Materials for the experiment
- Two coins per pair of pupils
- A pencil and the tally table
- Optional: stickers to mark the coins 'B' (heads) and 'b' (tails)
Safety: Toss coins gently on the table, not in the air near faces. Coins are small: keep them away from very young children.
Common misconceptions
| Pupils may think… | Actually… |
|---|---|
| Genes and chromosomes are different substances from DNA. | Genes are sections of DNA, and each chromosome holds one long DNA molecule. |
| A 1:2:1 ratio means every family of four has exactly that mix. | Ratios are chances; small samples often differ from them. |
| Each child gets all of one parent's DNA. | Each child gets one chromosome of each pair from each parent: half from each. |
Worksheet answers
- Nucleus, chromosome, gene.
- T T A C G G.
- Answers vary; the class total is usually close to 1:2:1 (for example about 25% BB, 50% Bb, 25% bb).
- Chance evens out over many tries, so a larger sample usually gets closer to the expected ratio.
Quiz answers
- Where is most DNA kept in an animal cell? In the nucleus. DNA is packed into chromosomes in the nucleus.[1]
- How many chromosomes do human cells have? 46, in 23 pairs. Humans have 22 numbered pairs plus one pair of sex chromosomes.[4]
- What is a gene? A section of DNA that is a unit of heredity. Genes are made of DNA and are passed from parents to children.[3]
- If one strand reads A T G C, the partner strand reads… T A C G. A pairs with T and G pairs with C.[1]
- What are alleles? Different versions of the same gene. Alleles are forms of a gene with small differences.[3]
- Two Bb parents: what share of babies is expected to be bb? One quarter. The expected ratio is 1 BB : 2 Bb : 1 bb.[5]
Going further
Repeat the coin toss with one parent BB (both coins marked B) and one parent Bb. Predict first: can any baby be bb?
Sources used in this lesson
- [1] Deoxyribonucleic Acid (DNA) Fact Sheet (National Human Genome Research Institute (NIH)): reliability High
- [2] What is DNA? (MedlinePlus Genetics, U.S. National Library of Medicine): reliability High
- [3] What is a gene? (MedlinePlus Genetics, U.S. National Library of Medicine): reliability High
- [4] Chromosome (Talking Glossary of Genomic and Genetic Terms) (National Human Genome Research Institute (NIH)): reliability High
- [5] Concepts of Biology, 8.2 Laws of Inheritance (OpenStax, Rice University): reliability High
Full list with links and a note on each source's reliability: echoesof.science/school/dna/sources/
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