Edexcel IGCSE Biology 3 18b Protein Synthesis Questions
Trace how mRNA carries a copied gene to a ribosome, where tRNA matches amino acids to codons to build a protein.
- Syllabus
- First assessment 2019
- Course
- Biology 4BI1
Exam points
- Describe transcription: DNA unwinds and one strand acts as a template for complementary mRNA, which is produced in the nucleus.
- Describe translation at a ribosome: mRNA codons pair with tRNA anticodons, tRNA brings amino acids, and the amino acids join into a polypeptide.
- Use the triplet code to relate bases to amino acids, including non-overlapping and alternative codons, and calculate base or amino-acid counts.
- Explain how RNA binding to mRNA can prevent translation and reduce or stop production of a specific protein.
Edexcel IGCSE Biology 3 18b Protein Synthesis Questions question 1
[Maximum number: 4]
Apples contain an enzyme called phenol oxidase.
When apple tissue is exposed to oxygen in the air, this enzyme turns the apple tissue brown.
A genetically modified (GM) variety of apple has been produced that does not turn brown when exposed to air.
These apples have a gene in their DNA that produces a section of mRNA with a complementary sequence to the mRNA for the phenol oxidase gene.
Explain why these GM apples do not turn brown when the apple tissue is exposed to air.
Use your knowledge of protein synthesis to support your answer.
An explanation that makes reference to four of the following points:
1. (complementary) RNA binds to the phenol oxidase RNA / eq
2. translation cannot occur
3. so enzyme / phenol oxidase not made
AND
max three from:
4. transcription makes (m)RNA
5. RNA leaves nucleus and enters cytoplasm / RNA moves to ribosome / eq
6. tRNA brings / carries / transports amino acids / eq
7. (during translation) tRNA binds mRNA / anticodons bind codons
8. amino acids join / amino acid chain / makes polypeptide / peptide bonds form / eq
Accept DNA unzips and
(m)RNA is
made
polymerase
makes (m)RNA
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