WHAT THIS MODEL HELPS US SEE
The manipulable ladder makes complementary pairing and two-strand structure visible and checkable.
LAUNCH · GCSE Biology · Lesson 14 of 18 · ExploreLAUNCH · GCSE Biology · Week 12 · Explore
DNA Structure: Pair, Twist, Critique
Sequence outcome: Describe DNA as a polymer of nucleotides arranged as two strands coiled into a double helix, with complementary base pairs joined by weak hydrogen bonds.
🎯 Learning objective: I can construct a complementary DNA section and describe the strengths and limitations of the model.
✅ Success criteria
- I can state that DNA has two strands coiled into a double helix.
- I can apply A-T and C-G complementary base pairing.
- I can identify at least one model strength and limitation.
Arrival · previous learningStarter · observe / predictI Do · model the reasoningWe Do · hinge & responseI Do 2 · connect / extendWe Do 2 · scientific model / dataIndependent · evidence & transferExit · receive and use the response
🧪 Base-Pair Lab: build a section of DNA and say what the model leaves out.⏱ 40 minutes📍 C42 only🔁 Live Lundy loop↺ Retry without penalty
QUESTIONEVIDENCEPATTERNEXPLANATIONAPPLICATIONEVALUATION
LAUNCH rule: explanation is earned through prediction, observation, measurement, calculation or reasoning from evidence.
🛡 SPACE
🗣 VOICE
👂 AUDIENCE
⚙ INFLUENCE
SPACE available · VOICE waiting · AUDIENCE waiting · INFLUENCE waiting
⏱ 3 min
🚪 Arrival · previous learningRetrieve only what has already been taught
- W12L1: a gene is a section of DNA.
- W12L1: chromosomes contain long DNA molecules.
- Lessons 1–3: copied genetic information is separated during mitosis.
- Lead-in: if one DNA strand reads A-C-G-T, what pattern might constrain the other?
New to this class, absent, or not sure? Everything needed is in the retrieval box above. Read it, point to it or ask a familiar adult to read it exactly.
◆ Supported
- Point to GENE inside DNA.
- Complete: chromosomes contain __.
- Choose: DNA has one strand or two strands?
- Lead-in: match A with T.
▲ Standard
- Describe the chromosome-DNA-gene relationship.
- Define genome.
- State one limit of the hierarchy model.
- Lead-in: predict the partner for base C.
★ Stretch
- Explain why a gene is not a whole chromosome.
- Correct the permanent-X chromosome model.
- Relate DNA sequence to genetic information without describing protein synthesis stages.
- Lead-in: explain why complementary means constrained, not identical.
LAUNCH response routes
📝 write / edit🗣 structured verbal📏 measure / calculate📊 graph / interpret🧪 practical / demonstrate↺ re-attempt
Access changes the response route, not the GCSE Biology entitlement.
🔊 Read-aloud route: a familiar adult may read the task exactly while the text remains visible. No device voice or media permission is required.
QUESTIONEVIDENCEPATTERNEXPLANATIONAPPLICATIONEVALUATION
LAUNCH rule: explanation is earned through prediction, observation, measurement, calculation or reasoning from evidence.
🛡 SPACE
🗣 VOICE
👂 AUDIENCE
⚙ INFLUENCE
SPACE available · VOICE waiting · AUDIENCE waiting · INFLUENCE waiting
⏱ 4 min
🌱 Starter · observe / predictOne DNA strand reads A-C-G-T. Which complementary strand fits the pairing rule?
LOCAL VISUAL HOOK · FRAME 1
A pairs with T
Adenine always faces thymine.
LOCAL VISUAL HOOK · FRAME 2
C pairs with G
Cytosine always faces guanine.
LOCAL VISUAL HOOK · FRAME 3
Two paired strands coil into a double helix
The model shows pairing and shape. Colours and sizes are invented.
Commit one first idea. Predictions are held, not marked. Pointing, selecting, saying or signing all count.
Choose one idea. The lesson will test it; nothing is scored or saved.
QUESTIONEVIDENCEPATTERNEXPLANATIONAPPLICATIONEVALUATION
LAUNCH rule: explanation is earned through prediction, observation, measurement, calculation or reasoning from evidence.
🛡 SPACE
🗣 VOICE
👂 AUDIENCE
⚙ INFLUENCE
SPACE available · VOICE waiting · AUDIENCE waiting · INFLUENCE waiting
⏱ 4 min
👩🏫 I Do · model the reasoningMake the first scientific idea visible
NUCLEOTIDEone DNA building unita sugar, phosphate group and one base
COMPLEMENTARYfits by a pairing rulematching by the fixed base pairs A-T and C-G
DOUBLE HELIXtwo-strand twistthe coiled shape formed by DNA's two strands
WHAT THIS MODEL DOES NOT SHOW
The model is enormously enlarged, uses arbitrary colours, simplifies chemical bonds and cannot show the full chromosome or molecular dynamics.
Step 1
DNA is a polymer of nucleotides. Each nucleotide contains a sugar, a phosphate group and one base; nucleotides join to form each sugar-phosphate backbone.
Step 2
Build the second strand using complementary base pairs: adenine (A) pairs with thymine (T), and cytosine (C) with guanine (G); weak hydrogen bonds join each pair between the strands.
Step 3
Twist the paired ladder gently to represent the double helix while keeping the base order visible.
Word help keeps the scientific term visible and adds a plain-language bridge.
🧬 Build the second strand
Strand 1 reads A T G C C A. Press the complementary base for each position.
1 · A pairs with…
2 · T pairs with…
3 · G pairs with…
4 · C pairs with…
5 · C pairs with…
6 · A pairs with…
Strand 2: _ _ _ _ _ _
Limit of the model: real bases are not coloured blocks, and the helix is far longer — this section is six of about three billion pairs.
QUESTIONEVIDENCEPATTERNEXPLANATIONAPPLICATIONEVALUATION
LAUNCH rule: explanation is earned through prediction, observation, measurement, calculation or reasoning from evidence.
🛡 SPACE
🗣 VOICE
👂 AUDIENCE
⚙ INFLUENCE
SPACE available · VOICE waiting · AUDIENCE waiting · INFLUENCE waiting
⏱ 4 min
🤝 We Do · hinge & responseA short strand reads G-A-T-C. Which complementary sequence is correct?
Everyone commits before explanation.
Use a button, point, say/sign or let an adult operate the chosen button. A retry is information, not a penalty.
Choose one response, then use the model to explain or retry.
Audience move: the adult names back the Science heard or seen, without upgrading the pupil’s words.
QUESTIONEVIDENCEPATTERNEXPLANATIONAPPLICATIONEVALUATION
LAUNCH rule: explanation is earned through prediction, observation, measurement, calculation or reasoning from evidence.
🛡 SPACE
🗣 VOICE
👂 AUDIENCE
⚙ INFLUENCE
SPACE available · VOICE waiting · AUDIENCE waiting · INFLUENCE waiting
⏱ 4 min
👩🏫 I Do 2 · connect / extendConnect the model to the second idea
Connection: the model is useful when its visible pattern is translated into a scientific explanation.
Connection 1
Strength: the ladder shows two strands, base order and complementary pairing clearly.
Connection 2
Limit: colours, distances and component sizes are invented; a classroom twist is not the molecule's true scale or movement.
Connection 3
A gene is a particular sequence along DNA; do not add Higher-tier transcription or translation stages to this Foundation lesson.
MODEL STRENGTH
The manipulable ladder makes complementary pairing and two-strand structure visible and checkable.
MODEL LIMIT
The model is enormously enlarged, uses arbitrary colours, simplifies chemical bonds and cannot show the full chromosome or molecular dynamics.
QUESTIONEVIDENCEPATTERNEXPLANATIONAPPLICATIONEVALUATION
LAUNCH rule: explanation is earned through prediction, observation, measurement, calculation or reasoning from evidence.
🛡 SPACE
🗣 VOICE
👂 AUDIENCE
⚙ INFLUENCE
SPACE available · VOICE waiting · AUDIENCE waiting · INFLUENCE waiting
⏱ 5 min
🤝 We Do 2 · scientific model / dataComplementary base-pair lab
Match each base to its complementary partner, freeze the sequence, then critique one feature of the model.
READPAIRCHECKTWISTCRITIQUE
Cards to place
Matching groups
No pair placed. Apply A-T and C-G before twisting the model.
🧩 Science glitch · find and repair it
Claim: Complementary DNA strands have exactly the same base sequence.
The incorrect idea is shown as a challenge, never as teaching.
QUESTIONEVIDENCEPATTERNEXPLANATIONAPPLICATIONEVALUATION
LAUNCH rule: explanation is earned through prediction, observation, measurement, calculation or reasoning from evidence.
🛡 SPACE
🗣 VOICE
👂 AUDIENCE
⚙ INFLUENCE
SPACE available · VOICE waiting · AUDIENCE waiting · INFLUENCE waiting
⏱ 12 min
✏️ Independent · evidence & transferConstruct a complementary DNA section, annotate its structure and evaluate the model.
👐 Physical route
Large nucleotide/base cards, reusable backbone strips, clips or hook-and-loop tabs, sequence sheet and pencil.
Same outcome: I can construct a complementary DNA section and describe the strengths and limitations of the model.
🖥 Offline digital / director route
Use the local button-only pairing lab with the same sequence and model critique.
Same evidence: A correct complementary sequence, labelled two-strand/double-helix description and one valid model limitation.
🧰 Equipment / setupLarge nucleotide/base cards, reusable backbone strips, clips or hook-and-loop tabs, sequence sheet and pencil.
🛡 Safety / sensoryUse large components and avoid latex or small clips where local needs require. Do not wrap the model around a person.
🖥 Offline parityUse the local button-only pairing lab with the same sequence and model critique.
No-equipment/access route: Direct an adult to place each base or point to the partner; dictate the sequence and model limitation.
◆ Supported
Complete a six-base sequence with A-T and C-G cards, then point to the two strands.
Scaffold
Pairing key stays visible; one base at a time and exact scribing are allowed.
▲ Standard
Complete a ten-base complementary sequence and describe nucleotide, two strands and double helix.
Scaffold
Use: Base __ pairs with __; the two strands __.
★ Stretch
Construct and check the sequence, then evaluate two useful features and two limitations of the model.
Scaffold
Do not add Higher-tier protein synthesis; deepen model evaluation.
Evidence gate
1 · Pupil decisionPrediction, question, method or choice is visible.
2 · Observable evidenceA result, source note, model state or adult observation is preserved.
3 · Pupil meaningA correct complementary sequence, labelled two-strand/double-helix description and one valid model limitation.
QUESTIONEVIDENCEPATTERNEXPLANATIONAPPLICATIONEVALUATION
LAUNCH rule: explanation is earned through prediction, observation, measurement, calculation or reasoning from evidence.
🛡 SPACE
🗣 VOICE
👂 AUDIENCE
⚙ INFLUENCE
SPACE available · VOICE waiting · AUDIENCE waiting · INFLUENCE waiting
⏱ 4 min
🎫 Exit · receive and use the responseFinish with an edit or re-attempt on the existing work
Supported
Which base pairs with C?
Standard
Write the complement of A-G-C-T.
Stretch
State one strength and one limitation of today's DNA model.
Adult Audience
The familiar adult genuinely receives the pupil response, then says back the Science they heard or saw. The adult does not add a score or rewrite the pupil.
SPACE available · VOICE waiting · AUDIENCE waiting · INFLUENCE waiting
Receive the pupil’s Voice, complete real Audience, then choose what changes.
Session state is temporary. Reload clears responses; there is no account, upload or saved pupil identity.
QUESTIONEVIDENCEPATTERNEXPLANATIONAPPLICATIONEVALUATION
LAUNCH rule: explanation is earned through prediction, observation, measurement, calculation or reasoning from evidence.
🛡 SPACE
🗣 VOICE
👂 AUDIENCE
⚙ INFLUENCE
SPACE available · VOICE waiting · AUDIENCE waiting · INFLUENCE waiting