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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 is a thin layer around the cytoplasm? (chloroplasts / cell membrane / cell wall / nucleus) → cell membranePrompt: Think about which parts are only in plant cells.
  2. Cells: which statement is NOT true? (Animal cells have a cell wall. / Most plant cells have a large permanent vacuole. / Both plant and animal cells have a nucleus, cytoplasm and a cell membrane. / Bacterial cells have no nucleus.) → Animal cells have a cell wall.Prompt: Do plant cells respire?
  3. Which part of a cell contains the genetic material? (chloroplasts / cell membrane / nucleus / mitochondria) → nucleusPrompt: 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. Where is DNA found in an animal cell? (outside the cell / in the cell wall / in the chloroplasts / mainly in the nucleus) → mainly in the nucleusPrompt: It is the control centre of the cell.
  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?

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? (12 / 23 / 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 an egg cell? → 23Prompt: 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

    How many chromosomes are in a normal human body cell?

    • A. 92
    • B. 46 (23 pairs)
    • C. 23
    • D. 12

  2. Question 2

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

    Answer

  3. Question 3

    Where is DNA found in an animal cell?

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

  4. Question 4

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

    Answer

  5. Question 5

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

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

  6. Question 6

    What is a gene?

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

  7. Question 7

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

    Answer

  8. Question 8

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

    Answer

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Answer key: DNA, genes and chromosomes

  1. 1. B. 46 (23 pairs)

  2. 2. 46

  3. 3. B. mainly in the nucleus

  4. 4. 23

  5. 5. A. the structure of DNA

  6. 6. A. a section of DNA that codes for a protein

  7. 7. 46

  8. 8. 23