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Science lesson plan · 10th grade (Year 11 in England) · 30 minutes

Write complementary DNA and mRNA base sequences

Cells, genetics and evolution

CCSS NGSS.HS-LS1-1CCSS NGSS.HS-LS3-1England: GCSE Biology: Inheritance, variation and evolution (DNA structure)

Objective and success criteria

Students will: Write complementary DNA and mRNA base sequences.

  • 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: DNA, genes and chromosomes

Leads to: Substitution, insertion and deletion mutations; Calculate DNA base percentages (A = T, C = G)

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

Warm-up · 4 min

  • Quick retrieval from earlier learning (DNA, genes and chromosomes). Students answer on mini whiteboards.
  • Show answers together and note who needs support in the main task.
  1. How many chromosomes are in a normal human body cell? (46 (23 pairs) / 92 / 12 / 23) → 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?
  3. Where is DNA found in an animal cell? (mainly in the nucleus / outside the cell / in the cell wall / in the chloroplasts) → mainly in the nucleusPrompt: It is the control centre of the cell.

Hook · 3 min

  • Show a microscope image of cells and ask what students think they are looking at.
  • Share the objective: Write complementary DNA and mRNA base sequences. Read the success criteria together.

I do: model it · 7 min

  • Work through the example out loud, saying why you do each step, not just what you do.
  • Example: One strand of DNA reads TGT TCT CTA. Write the complementary DNA strand (letters only).
  • Step 1: TGTTCTCTA → ACAAGAGAT
  • Step 2: So the answer is: ACAAGAGAT
  • Answer: ACAAGAGAT
  • Pause after each step and ask a student to say what comes next.

We do: guided practice · 6 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. One strand of DNA reads CAA GGA CCA. Write the complementary DNA strand (letters only). → GTTCCTGGTPrompt: A always pairs with T in DNA.
  2. A DNA template strand reads GGA AAG CAG. Write the mRNA sequence transcribed from it (letters only). → CCUUUCGUCPrompt: RNA has uracil (U) instead of thymine (T).

You do: independent practice · 7 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 6 questions are on the student sheet below, with answers in the key.

Exit ticket · 3 min

  • Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.
  1. DNA is described as a double helix. What forms the "backbone" of each strand? (amino acids / fatty acids / pairs of bases / alternating sugar and phosphate groups) → alternating sugar and phosphate groupsPrompt: The bases point inwards like the rungs of a ladder.
  2. One strand of DNA reads TCC GCT. Write the complementary DNA strand (letters only). → AGGCGAPrompt: A always pairs with T in DNA.

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: DNA, genes and chromosomes.
  • 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: Substitution, insertion and deletion mutations; Calculate DNA base percentages (A = T, C = G).
  • 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-10.

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

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Write complementary DNA and mRNA base sequences

Name

Date

Score/ 6

  1. Question 1

    What holds the two strands of the DNA double helix together?

    • A. strong ionic bonds
    • B. weak hydrogen bonds between complementary base pairs
    • C. metal atoms
    • D. a layer of protein

  2. Question 2

    A DNA template strand reads TCG AGA. Write the mRNA sequence transcribed from it (letters only).

    Answer

  3. Question 3

    One strand of DNA reads ATA ATC ATC. Write the complementary DNA strand (letters only).

    Answer

  4. Question 4

    Which scientists' X-ray image helped show DNA is a double helix?

    • A. Louis Pasteur's
    • B. Alexander Fleming's
    • C. Gregor Mendel's
    • D. Rosalind Franklin's (with Maurice Wilkins's lab)

  5. Question 5

    A DNA template strand reads ACT CCG CTG. Write the mRNA sequence transcribed from it (letters only).

    Answer

  6. Question 6

    One strand of DNA reads CAT TCG. Write the complementary DNA strand (letters only).

    Answer

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Answer key: Write complementary DNA and mRNA base sequences

  1. 1. B. weak hydrogen bonds between complementary base pairs

  2. 2. AGCUCU

  3. 3. TATTAGTAG

  4. 4. D. Rosalind Franklin's (with Maurice Wilkins's lab)

  5. 5. UGAGGCGAC

  6. 6. GTAAGC