Describe mRNA passing through a ribosome
mRNA passes through the ribosome while a separate amino-acid chain is assembled. Counting completed stipulated passes can count model products; a passing message is not a moved chromosome.
Exam scope and assessment notes
Extended only (Supplement) · Biology 0970, 2026–2028. Use the stated specimen features and evidence. Diagrams are schematic. Written practice is self-checked; human subject-teacher review, supervised practical competence and cumulative assessment remain pending. Cambridge states that IGCSE 0970 has the same subject content as IGCSE 0610, with 9–1 grading. This StudyForA pathway maps the 2026–2028 syllabus only. This 9–1 graded qualification is available only in a limited number of administrative zones. Confirm that your centre can enter you for this code and exam series with Cambridge International. Cambridge has published a separate syllabus for 2029. StudyForA has not reconciled that version yet; this page supports exams in 2026, 2027 and 2028 only.
Before you begin
- Recall the nucleus, DNA base pairing, gametes, fertilisation, enzymes, membrane carriers and chemical synapses.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
What passes through the ribosome in the requirement?
What you will learn
- Locate the message used in protein assembly
- Separate the ribosome from the information source and product
Original teaching model. Counts and records are stipulated; drawings are schematic.
| Feature | Meaning |
|---|---|
| Information molecule | mRNA passes through ribosome |
| Machinery | Ribosome |
| Separate product | Growing amino-acid chain |
| Count condition | Completed assembly events, not partial passes |
Locate the message used in protein assembly
In the required protein-production sequence, mRNA passes through ribosomes. The ribosome is the assembly machinery using the message, not the DNA gene or the finished protein. The message’s base sequence carries the order information that guides assembly. The original nuclear gene remains at the source while the message is used in the cytoplasmic model.
A diagram can show a strand entering and leaving the ribosome with a growing amino-acid chain emerging separately. Label the strand mRNA and the growing chain protein or amino-acid chain. The two are different materials. A line passing through a ribosome is not automatically a chromosome, and the ribosome does not turn the message material into amino acids.
Separate the ribosome from the information source and product
One message can be used for more than one assembly event. If an original model stipulates three completed passes of the same message, each giving one chain, then it specifies three chain products under those conditions. Do not convert this limited event count into a rule that every message always makes exactly one protein or that incomplete passes count as completed products.
The original ribosome model is a schematic, not a measured molecular photograph. It shows the required message path and separate product material without detailed initiation, elongation or termination chemistry. The next lesson follows amino acids being assembled, so learners can explain both the information path and the material path.
Pause and explain
A model states three completed passes, each producing one chain. How many chains are specified?
Worked example
Which two labels distinguish the passing strand from the growing chain?
Show the worked solution
- Identify the message strand as mRNA.
- Identify the product chain as amino acids assembled into protein.
Answer mRNA passes through the ribosome; a separate amino-acid chain is assembled as the protein product.
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Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
Label the message passing through a ribosome and the separate growing product.
Give me a hint
Distinguish information molecule from assembled material.
Compare my reasoning
- Label the strand mRNA.
- Label the growing product amino-acid chain or protein.
The passing strand is mRNA; the separate growing product is an amino-acid chain forming a protein.
Look for these in your work
- Name the message
- Name the product material
Count products in a stipulated model of three completed message passes, each giving one chain.
Give me a hint
Count completed assembly events.
Compare my reasoning
- Use three completed passes.
- Apply one chain per stated pass.
The model specifies three chain products; it does not establish a universal fixed number per mRNA molecule.
Look for these in your work
- Use the completed event count
- Keep the stipulation
A sketch shows four partial passes but no completed chains. Can it prove four finished proteins?
Give me a hint
Completion is part of the product-count condition.
Compare my reasoning
- Identify partial rather than completed events.
- Reject counting every partial event as a completed product.
No. Four partial passes do not establish four finished proteins; completion evidence has not been supplied.
Look for these in your work
- Distinguish partial and complete
- Reject unsupported product count
Common mistakes
- The passing message is not the chromosome gene.
- A message can support more than one assembly event.
What can you explain now?
A model states three completed passes, each producing one chain. How many chains are specified?
Compare with the explanation
Three under the stated conditions
Each completed event gives one stated product.
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Make it stick
Explain locate the message used in protein assembly and separate the ribosome from the information source and product. Use the stated cell, chromosome sets and information pathway before opening the solutions.
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.