A spider produces silk protein in specialised glands. The silk protein has a specific sequence of amino acids that gives it its properties. Explain how the genetic information in a spider's cells controls the production of silk protein.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Spider silk is one of the strongest natural materials known. The silk is made of protein and is produced in silk glands found in the spider's abdomen. Scientists are interested in how the spider's genetic information leads to the production of this specific protein.
Model answer (5 marks)
A gene in the spider’s DNA, located in the nucleus, contains the instructions for the silk protein.
During transcription the gene is copied into mRNA, which carries the sequence of nucleotides out of the nucleus.
The mRNA then travels to the ribosome, where translation occurs: codons are read and the corresponding amino acids are joined together.
The resulting polypeptide has a specific amino‑acid sequence.
This sequence determines the protein’s three‑dimensional structure, which gives the silk its unique mechanical properties.
During transcription the gene is copied into mRNA, which carries the sequence of nucleotides out of the nucleus.
The mRNA then travels to the ribosome, where translation occurs: codons are read and the corresponding amino acids are joined together.
The resulting polypeptide has a specific amino‑acid sequence.
This sequence determines the protein’s three‑dimensional structure, which gives the silk its unique mechanical properties.
Examiner tips
- Use the word ‘gene’ and mention the nucleus; include transcription and translation; explain that the amino‑acid sequence dictates structure and properties; keep answer concise and structured.
- Use correct terminology (gene, DNA, mRNA, ribosome, codon, amino acid, polypeptide).
Common mistakes
- Confusing DNA with mRNA as the messenger; omitting the nucleus; not linking amino‑acid sequence to protein structure; using vague terms like ‘protein’ without specifying sequence.
Mark scheme (5 marks)
- A gene is a section of DNA that codes for a specific amino acid sequence
- The DNA/gene is found in the nucleus of the cell
- mRNA carries the genetic information from the nucleus to the ribosomes (transcription)
- At the ribosome, the mRNA sequence is translated into an amino acid sequence (translation)
- The specific sequence of amino acids determines the structure/shape of the silk protein and therefore its properties/function
Key terms in this question
Related
- All OCR A-Level Biology B — Advancing Biology (H422) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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