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Science lesson plan · 8th grade (Year 9 in England) · 60 minutes

DNA, genes and chromosomes

Cells, genetics and evolution

CCSS NGSS.MS-LS3-1CCSS NGSS.HS-LS1-1CCSS NGSS.HS-LS3-1England: KS3 Biology: Genetics and evolutionEngland: KS4 Combined Science: Evolution, inheritance and variation

Objective and success criteria

Students will: DNA, genes and chromosomes.

  • I can answer questions on today's skill on my own, without help.
  • I can explain each step and say why it works.
  • I can check my answer and spot a mistake.

Before and after

Needs first: Plant and animal cells

Leads to: Genetic crosses and Punnett squares; Mitosis and meiosis; Natural selection and resistance

Materials: Microscope images or slides, Cell diagrams, Mini whiteboards, A diagram or short video clip of the idea, Printed student sheet (below).

Warm-up · 6 min

  • Quick retrieval from earlier learning (Plant and animal cells). Students answer on mini whiteboards.
  • Show answers together and note who needs support in the main task.
  1. Which part of a cell releases energy from glucose? (cell wall / nucleus / mitochondria / chloroplasts) → mitochondriaPrompt: Think about which parts are only in plant cells.
  2. Cells: which statement is NOT true? (Bacterial cells have no nucleus. / Plant cells have a cell wall but animal cells do not. / Chloroplasts are found in plant cells, not animal cells. / Animal cells have a cell wall.) → Animal cells have a cell wall.Prompt: Do plant cells respire?
  3. Which part of a cell controls what enters and leaves the cell? (nucleus / chloroplasts / cell wall / cell membrane) → cell membranePrompt: Think about which parts are only in plant cells.

Hook · 6 min

  • Show a microscope image of cells and ask what students think they are looking at.
  • Share the objective: DNA, genes and chromosomes. Read the success criteria together.

I do: model it · 12 min

  • Work through the example out loud, saying why you do each step, not just what you do.
  • Example: What is a gene?
  • Step 1: A gene is a short section of DNA carrying the code for one protein.
  • Step 2: So the answer is: a section of DNA that codes for a protein
  • Answer: a section of DNA that codes for a protein
  • Pause after each step and ask a student to say what comes next.

We do: guided practice · 12 min

  • Do these together. Students try each step on whiteboards before you reveal it.
  • Use the hints as prompts rather than giving the answer.
  1. What shape is a DNA molecule? (a double helix / a ring of six atoms / a single straight line / a cube) → a double helixPrompt: It looks like a twisted ladder.
  2. Human body cells have 23 pairs of chromosomes. How many chromosomes are in an egg cell? → 23Prompt: Is this a gamete (sex cell) or a body cell?

You do: independent practice · 17 min

  • Students work on the student sheet. Circulate and check the first two answers of every student early.
  • Students who finish: write a question of their own for a partner, with the answer.

The 8 questions are on the student sheet below, with answers in the key.

Exit ticket · 7 min

  • Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.
  1. How many chromosomes are in a normal human body cell? (23 / 12 / 46 (23 pairs) / 92) → 46 (23 pairs)Prompt: They come in pairs, one of each pair from each parent.
  2. Human body cells have 23 pairs of chromosomes. How many chromosomes are in a muscle cell? → 46Prompt: Is this a gamete (sex cell) or a body cell?

Watch out for

  • Everyday meanings of words getting in the way of the science meaning: define key words explicitly.
  • Remembering facts without the reason: ask "why?" and "what is the evidence?"

Support and stretch

Support

  • Review first: Plant and animal cells.
  • Use concrete materials: microscope images or slides.
  • Give the first step of each question, or a partly worked example to finish.
  • Pair with a confident partner for the guided practice.

Stretch

  • Move on to: Genetic crosses and Punnett squares; Mitosis and meiosis; Natural selection and resistance.
  • Explain a common mistake in writing and how to fix it.
  • Write a word problem that uses today's skill, then solve a partner's.

Homework and more practice

Free online practice with hints and printable worksheets for this skill: eurekami.com/science/grade-8.

Free lesson plan from eurekami.com/lesson-plan-builder

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DNA, genes and chromosomes

Name

Date

Score/ 8

  1. Question 1

    Human body cells have 23 pairs of chromosomes. How many chromosomes are in an egg cell?

    Answer

  2. Question 2

    Where is DNA found in an animal cell?

    • A. outside the cell
    • B. in the cell wall
    • C. in the chloroplasts
    • D. mainly in the nucleus

  3. Question 3

    Rosalind Franklin's X-ray image helped scientists discover…

    • A. the first vaccine
    • B. the structure of DNA
    • C. penicillin
    • D. the shape of the Earth

  4. Question 4

    Human body cells have 23 pairs of chromosomes. How many chromosomes are in a skin cell?

    Answer

  5. Question 5

    What is a gene?

    • A. a disease
    • B. a section of DNA that codes for a protein
    • C. a type of cell
    • D. a whole chromosome

  6. Question 6

    Human body cells have 23 pairs of chromosomes. How many chromosomes are in a muscle cell?

    Answer

  7. Question 7

    Human body cells have 23 pairs of chromosomes. How many chromosomes are in a sperm cell?

    Answer

  8. Question 8

    What shape is a DNA molecule?

    • A. a ring of six atoms
    • B. a cube
    • C. a double helix
    • D. a single straight line

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Answer key: DNA, genes and chromosomes

  1. 1. 23

  2. 2. D. mainly in the nucleus

  3. 3. B. the structure of DNA

  4. 4. 46

  5. 5. B. a section of DNA that codes for a protein

  6. 6. 46

  7. 7. 23

  8. 8. C. a double helix