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Science lesson plan · 11th grade (Year 12 in England) · 45 minutes

Substitution, insertion and deletion mutations

Cells, genetics and evolution

CCSS NGSS.HS-LS3-2England: GCSE Biology: Inheritance, variation and evolution (mutations)

Objective and success criteria

Students will: Substitution, insertion and deletion mutations.

  • 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: Write complementary DNA and mRNA base sequences

Leads to: the next skill in this area.

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

Warm-up · 5 min

  • Quick retrieval from earlier learning (Write complementary DNA and mRNA base sequences). Students answer on mini whiteboards.
  • Show answers together and note who needs support in the main task.
  1. One strand of DNA reads ATA CTT. Write the complementary DNA strand (letters only). → TATGAAPrompt: A always pairs with T in DNA.
  2. A DNA template strand reads CTT AGA ACT. Write the mRNA sequence transcribed from it (letters only). → GAAUCUUGAPrompt: RNA has uracil (U) instead of thymine (T).
  3. DNA is described as a double helix. What forms the "backbone" of each strand? (amino acids / pairs of bases / fatty acids / alternating sugar and phosphate groups) → alternating sugar and phosphate groupsPrompt: The bases point inwards like the rungs of a ladder.

Hook · 5 min

  • Show a microscope image of cells and ask what students think they are looking at.
  • Share the objective: Substitution, insertion and deletion mutations. Read the success criteria together.

I do: model it · 10 min

  • Work through the example out loud, saying why you do each step, not just what you do.
  • Example: Original DNA: ACT GAG GGT Mutated DNA: ACT TAG GGT What type of mutation is this?
  • Step 1: Original: 9 bases. Mutated: 9 bases.
  • Step 2: So the answer is: substitution
  • Answer: substitution
  • Pause after each step and ask a student to say what comes next.

We do: guided practice · 10 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. Original DNA: TGA GCT CGT Mutated DNA: TGA GCT ACG T What type of mutation is this? (substitution / insertion / deletion) → insertionPrompt: Count the bases in each sequence.
  2. Sickle cell disease is caused by a single base substitution in the haemoglobin (hemoglobin) gene. What is the effect? (One amino acid changes, altering the protein's shape and red blood cell shape / Red blood cells gain a nucleus / The whole haemoglobin gene is deleted / No change at all) → One amino acid changes, altering the protein's shape and red blood cell shapePrompt: One different amino acid can change how a protein folds.

You do: independent practice · 10 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 · 5 min

  • Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.
  1. Original DNA: CGC TGT CCA Mutated DNA: CGC GGT CCA What type of mutation is this? (substitution / insertion / deletion) → substitutionPrompt: Count the bases in each sequence.
  2. Mutations: which statement is NOT true? (Ionising radiation can increase the rate of mutation. / Mutations in skin cells are passed on to children. / A mutation is a change in the DNA base sequence. / Mutations provide the variation that natural selection acts on.) → Mutations in skin cells are passed on to children.Prompt: Are all mutations harmful?

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: Write complementary DNA and mRNA base sequences.
  • 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

  • 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-11.

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

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Substitution, insertion and deletion mutations

Name

Date

Score/ 8

  1. Question 1

    Mutations: which statement is NOT true?

    • A. Mutations happen randomly and continuously.
    • B. All mutations are harmful.
    • C. Mutations provide the variation that natural selection acts on.
    • D. Ionising radiation can increase the rate of mutation.

  2. Question 2

    Original DNA: GTG CTC AGG Mutated DNA: GTG ATC AGG What type of mutation is this?

    • A. substitution
    • B. insertion
    • C. deletion

  3. Question 3

    Sickle cell disease is caused by a single base substitution in the haemoglobin (hemoglobin) gene. What is the effect?

    • A. The whole haemoglobin gene is deleted
    • B. One amino acid changes, altering the protein's shape and red blood cell shape
    • C. Red blood cells gain a nucleus
    • D. No change at all

  4. Question 4

    Original DNA: TTG CCT ATG Mutated DNA: TTG CCA TG What type of mutation is this?

    • A. substitution
    • B. insertion
    • C. deletion

  5. Question 5

    Why does a deletion usually have a bigger effect than a substitution?

    • A. It changes only one amino acid
    • B. It removes a whole chromosome
    • C. It always makes the protein longer
    • D. It shifts the reading frame, changing every codon after it

  6. Question 6

    Original DNA: GTA GAA GAG Mutated DNA: GTA GAA AAG What type of mutation is this?

    • A. substitution
    • B. insertion
    • C. deletion

  7. Question 7

    Most mutations…

    • A. are caused only by radiation
    • B. are always helpful
    • C. have little or no effect on the phenotype
    • D. are always harmful

  8. Question 8

    Original DNA: TTA CAC CGC Mutated DNA: TTA CTA CCG C What type of mutation is this?

    • A. substitution
    • B. insertion
    • C. deletion

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Answer key: Substitution, insertion and deletion mutations

  1. 1. B. All mutations are harmful.

  2. 2. A. substitution

  3. 3. B. One amino acid changes, altering the protein's shape and red blood cell shape

  4. 4. C. deletion

  5. 5. D. It shifts the reading frame, changing every codon after it

  6. 6. A. substitution

  7. 7. C. have little or no effect on the phenotype

  8. 8. B. insertion