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Science lesson plan · 10th grade (Year 11 in England) · 45 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 · 5 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. Where is DNA found in an animal cell? (outside the cell / mainly in the nucleus / in the cell wall / in the chloroplasts) → 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 sperm cell? → 23Prompt: Is this a gamete (sex cell) or a body cell?
  3. What shape is a DNA molecule? (a ring of six atoms / a double helix / a cube / a single straight line) → a double helixPrompt: It looks like a twisted ladder.

Hook · 5 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 · 10 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 · 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. One strand of DNA reads CGA AAT. Write the complementary DNA strand (letters only). → GCTTTAPrompt: A always pairs with T in DNA.
  2. A DNA template strand reads AAT GTG TGC. Write the mRNA sequence transcribed from it (letters only). → UUACACACGPrompt: RNA has uracil (U) instead of thymine (T).

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. A DNA template strand reads GAT AAT. Write the mRNA sequence transcribed from it (letters only). → CUAUUAPrompt: RNA has uracil (U) instead of thymine (T).
  2. What holds the two strands of the DNA double helix together? (metal atoms / strong ionic bonds / a layer of protein / weak hydrogen bonds between complementary base pairs) → weak hydrogen bonds between complementary base pairsPrompt: The bonds must break easily when DNA unzips.

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/ 8

  1. Question 1

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

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

  2. Question 2

    A DNA template strand reads ACC AGG TGC. Write the mRNA sequence transcribed from it (letters only).

    Answer

  3. Question 3

    One strand of DNA reads GTA GAC AGA. Write the complementary DNA strand (letters only).

    Answer

  4. Question 4

    Which base is found in RNA but not in DNA?

    • A. uracil (U)
    • B. guanine (G)
    • C. thymine (T)
    • D. adenine (A)

  5. Question 5

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

    Answer

  6. Question 6

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

    Answer

  7. Question 7

    DNA is described as a double helix. What forms the "backbone" of each strand?

    • A. alternating sugar and phosphate groups
    • B. fatty acids
    • C. amino acids
    • D. pairs of bases

  8. Question 8

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

    Answer

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Answer key: Write complementary DNA and mRNA base sequences

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

  2. 2. UGGUCCACG

  3. 3. CATCTGTCT

  4. 4. A. uracil (U)

  5. 5. UUGGACUCA

  6. 6. GGCTAG

  7. 7. A. alternating sugar and phosphate groups

  8. 8. CUUUAC