1. Release
What does detergent help to disrupt?
Help beside the question
Read or point first. Cell and nuclear boundaries.
Answer guidance
Membranes.
Fruit DNA: extract, observe, evaluate
Learning objective
Explain the roles of extraction steps and distinguish an observation of a crude extract from a claim about purity.
40 minutes · one route · start from what you show today. Point, speak, sign, draw, write or direct an adult. An adult may read or scribe your exact words. Choose one route; do not complete all three.
LAUNCH · GCSE BIOLOGY FOUNDATION · W12 · LESSON 3 · 4 MINUTES
Four clues to start
Supported · 4 questions
2. Filter
What does filtering remove?
Help beside the question
Read or point first. Large tissue pieces or individual genes?
Answer guidance
Larger tissue debris.
3. Observe
Is “white strands appeared” an observation or a purity test?
Help beside the question
Read or point first. It describes what was seen.
Answer guidance
An observation.
4. Safety
Who handles and layers the cold ethanol in this route?
Help beside the question
Read or point first. Use the adult-directed method.
Answer guidance
The trained adult, following the centre’s risk assessment.
Standard · 4 questions
1. Release
What does detergent help to disrupt?
Help beside the question
Cell and nuclear boundaries.
Answer guidance
Membranes.
2. Filter
What does filtering remove?
Help beside the question
Large tissue pieces or individual genes?
Answer guidance
Larger tissue debris.
3. Observe
Is “white strands appeared” an observation or a purity test?
Help beside the question
It describes what was seen.
Answer guidance
An observation.
4. Safety
Who handles and layers the cold ethanol in this route?
Help beside the question
Use the adult-directed method.
Answer guidance
The trained adult, following the centre’s risk assessment.
Stretch · 4 questions
1. Release
What does detergent help to disrupt?
Help beside the question
Cell and nuclear boundaries.
Answer guidance
Membranes.
2. Filter
What does filtering remove?
Help beside the question
Large tissue pieces or individual genes?
Answer guidance
Larger tissue debris.
3. Observe
Is “white strands appeared” an observation or a purity test?
Help beside the question
It describes what was seen.
Answer guidance
An observation.
4. Safety
Who handles and layers the cold ethanol in this route? Give a reason.
Help beside the question
Use the adult-directed method.
Answer guidance
The trained adult, following the centre’s risk assessment. Accept a scientifically correct reason that uses the relevant model or evidence.
LAUNCH · GCSE BIOLOGY FOUNDATION · W12 · LESSON 3 · 3 MINUTES
Choose a first idea
White, stringy material appears. Which statement is most careful?
Think or discuss first. No answer chosen yet.
LAUNCH · GCSE BIOLOGY FOUNDATION · W12 · LESSON 3 · 4 MINUTES
Watch the model
Gently mash soft fruit in a sealed bag with the centre-approved extraction solution.
Worked explanation · reveal after thinking
Non-core fruit-DNA practical aligned to specification 3.6. Use the centre-approved method, technician preparation and local risk assessment. Appearance alone does not prove purity or measure DNA yield. Individual genes or a double helix cannot be seen with the naked eye.
32-second silent captioned explainer · optional
No sound or autoplay. Use instead of part of the modelling time, not as an extra activity.
Full transcript
Break up the tissue. Gently mash soft fruit in a sealed bag with the centre-approved extraction solution.
Release the contents. Detergent helps disrupt membranes. Salt assists the extraction and precipitation process.
Remove large debris. Filter the mixture. The liquid contains dissolved and suspended material released from the fruit.
Observe the interface. An adult carefully layers cold ethanol. White, stringy material may appear; it is a crude DNA-containing extract.
LAUNCH · GCSE BIOLOGY FOUNDATION · W12 · LESSON 3 · 4 MINUTES
Sort using the evidence
Choose a card, then choose a group. Explain one placement using its clue.
Drag, or use Tab and Enter to select a card and its group. Pointing or adult-directed placement works too.
Release contents
Separate material
Observe and evaluate
Choose a card first.
Read the card clues
Mash soft fruit: Break up tissue and expose cells.
Add approved detergent–salt solution: Disrupt membranes and assist extraction.
Filter the mixture: Remove larger tissue debris.
Adult layers cold ethanol: Help DNA precipitate from solution.
Record white stringy material: State the appearance without claiming purity.
Name one contamination limit: Crude extract may contain other material.
Would a small change help? · optional
Ask the lesson teacher for clearer labels, fewer cards, reading help, an adult-directed model or more thinking time. Your teacher will explain what can change, try it and check its effect. Ask privately or pass; no extra form is needed.
Group explanations · reveal after sorting
Mash soft fruit → Release contents. Break up tissue and expose cells.
Add approved detergent–salt solution → Release contents. Disrupt membranes and assist extraction.
Filter the mixture → Separate material. Remove larger tissue debris.
Adult layers cold ethanol → Separate material. Help DNA precipitate from solution.
Record white stringy material → Observe and evaluate. State the appearance without claiming purity.
Name one contamination limit → Observe and evaluate. Crude extract may contain other material.
LAUNCH · GCSE BIOLOGY FOUNDATION · W12 · LESSON 3 · 3 MINUTES
Work through one example
Worked example
After filtering, a liquid looks clear. Does that prove it contains only DNA?
Step 1
The observation is appearance: the liquid looks clear.
Step 2
Filtering removed large debris, not every dissolved substance.
Step 3
Other molecules may remain even when they are not visible.
Step 4
Therefore a clear filtrate is not evidence of pure DNA.
LAUNCH · GCSE BIOLOGY FOUNDATION · W12 · LESSON 3 · 4 MINUTES
Practical or supplied-observation route
Follow the centre-approved method with adult handling of ethanol, or use the fictional observations below. Keep observed and supplied evidence clearly distinct.
| Sample | Observation after layering ethanol |
|---|---|
| Fruit extract | White stringy material at the liquid boundary |
| Water comparison | No visible strands |
| Limit | No chemical purity test was performed |
Teacher-approved practical or observation route
Teacher/technician must approve the local method, concentrations, quantities, PPE and disposal. Use soft fruit prepared by an adult, sealed bags and a tray. Check allergies without requiring public disclosure. No tasting. Adult handles cold ethanol; keep it away from flames, sparks and heat. Do not use human samples or mouth pipetting. Observation and supplied-data routes are equal alternatives.
- Gently mash soft fruit in a sealed bag with the centre-approved extraction solution.
- Detergent helps disrupt membranes. Salt assists the extraction and precipitation process.
- Filter the mixture. The liquid contains dissolved and suspended material released from the fruit.
- An adult carefully layers cold ethanol. White, stringy material may appear; it is a crude DNA-containing extract.
Worked explanation · reveal after thinking
The observation is consistent with a DNA-containing precipitate from the fruit extract. The water comparison helps show that strands did not simply appear in every tube. It does not identify all substances or prove purity.
LAUNCH · GCSE BIOLOGY FOUNDATION · W12 · LESSON 3 · 14 MINUTES
Show your understanding
Supported · choose one route
1. Explain
Link mashing, detergent, filtering and ethanol to their roles.
Use the step cards: mash / detergent / filter / cold ethanol. Match each step to its stated purpose.
2. Record
Write an observation and a cautious interpretation using your evidence route.
Choose actual demonstration or supplied observations. Complete: I observed ___; this may indicate ___.
3. Evaluate
Give one limitation and one useful comparison or improvement.
Complete: the appearance supports a crude extract, but does not prove ___. One useful extra check would be ___.
Standard · choose one route
1. Explain
Link mashing, detergent, filtering and ethanol to their roles.
Use release, remove debris and precipitate.
2. Record
Write an observation and a cautious interpretation using your evidence route.
Start “I observed…” or “The supplied record states…”.
3. Evaluate
Give one limitation and one useful comparison or improvement.
Purity, equal fruit mass, same volumes or a water comparison.
Stretch · choose one route
1. Explain
Link mashing, detergent, filtering and ethanol to their roles.
Use release, remove debris and precipitate.
2. Record
Write an observation and a cautious interpretation using your evidence route.
Start “I observed…” or “The supplied record states…”.
3. Fair comparison
Two groups get different amounts of visible material. Why is this not automatically a fair comparison of DNA yield?
Think fruit mass, volumes, mixing, timing and purity.
LAUNCH · GCSE BIOLOGY FOUNDATION · W12 · LESSON 3 · 4 MINUTES
Two small checks
Supported · 2 questions
1. Role
Why is detergent used in fruit-DNA extraction?
Help beside the question
Use: my answer is ___ because ___. Point to a model or card first. Think membranes and released contents.
Answer guidance
It helps disrupt membranes, releasing cell contents including DNA.
2. Limit
Why should the visible material not be called pure DNA?
Help beside the question
Use: the evidence shows ___, but cannot yet show ___. Consider what else may be present.
Answer guidance
The crude extract may contain other cell material; appearance alone does not establish purity.
Standard · 2 questions
1. Role
Why is detergent used in fruit-DNA extraction?
Help beside the question
Think membranes and released contents.
Answer guidance
It helps disrupt membranes, releasing cell contents including DNA.
2. Limit
Why should the visible material not be called pure DNA?
Help beside the question
Consider what else may be present.
Answer guidance
The crude extract may contain other cell material; appearance alone does not establish purity.
Stretch · 2 questions
1. Role
Why is detergent used in fruit-DNA extraction?
Help beside the question
Think membranes and released contents.
Answer guidance
It helps disrupt membranes, releasing cell contents including DNA.
2. Fair comparison
Two groups get different amounts of visible material. Why is this not automatically a fair comparison of DNA yield?
Help beside the question
Think fruit mass, volumes, mixing, timing and purity.
Answer guidance
Different conditions or contaminants may affect visible material. Standardise conditions and use an appropriate DNA measurement before comparing true yield.
Keep one useful science explanation. No additional participation record is required.