Free Nucleic acids & protein synthesis questions for AS Level Biology (9700), part of Cells & molecules. Each question has the answer and the marking points an examiner would look for.
Generate a full Nucleic Acids & Protein Synthesis worksheet →All Cells & molecules questionsThe base sequence of part of the template strand of a gene is CAT GGT ACC.
What is the base sequence of the mRNA transcribed from it?
Answer: B
Which row describes tRNA?
| binds amino acid at | contains | site of action | |
|---|---|---|---|
| A | 3′ end | a codon | ribosome |
| B | 3′ end | an anticodon | nucleus |
| C | 5′ end | an anticodon | ribosome |
| D | 3′ end | an anticodon | ribosome |
Answer: D
Which term is described by this statement?
“Synthesis of mRNA using a DNA template.”
Answer: A
In a sample of double-stranded DNA, 18% of the nucleotides contain adenine.
What percentage contain cytosine?
Answer: B
This question is about DNA and protein synthesis.
Describe the structure of a DNA nucleotide and how nucleotides join to form a polynucleotide.
The template strand of part of a gene has the sequence TACGGATCA. Write the mRNA sequence transcribed from it.
Describe transcription.
Explain why a substitution mutation may have no effect on the protein produced.
State the role of tRNA in translation.
| Part | Answer and marking points | Marks |
|---|---|---|
| (a) | deoxyribose, phosphate, nitrogenous base; condensation; phosphodiester bonds between sugar and phosphate nucleotide: deoxyribose, a phosphate group and a nitrogenous base B1 condensation reactions join nucleotides B1 forming phosphodiester bonds (sugar–phosphate backbone) B1 | 3 |
| (b) | AUGCCUAGU AUGCCUAGU B1 | 1 |
| (c) | DNA unwinds, H bonds break; RNA polymerase; free RNA nucleotides pair with template; phosphodiester bonds; mRNA leaves via nuclear pore part of the DNA unwinds and hydrogen bonds between bases break B1 free RNA nucleotides pair with complementary bases on the template strand (A with U) B1 RNA polymerase joins them with phosphodiester bonds B1 mRNA detaches and leaves through a nuclear pore B1 | 4 |
| (d) | degenerate code: several triplets code for same amino acid the genetic code is degenerate B1 the new triplet may code for the same amino acid B1 | 2 |
| (e) | carries specific amino acid; anticodon pairs with mRNA codon each tRNA carries a specific amino acid B1 its anticodon pairs with the complementary codon on the mRNA at the ribosome B1 | 2 |
Protein synthesis involves transcription and translation.
Describe the process of transcription.
Explain the role of tRNA in translation.
| Part | Answer and marking points | Marks |
|---|---|---|
| (a) | RNA polymerase; complementary base pairing; mRNA leaves nucleus DNA unwinds and hydrogen bonds break B1 one strand is the template B1 RNA polymerase joins free RNA nucleotides by complementary base pairing (A–U) B1 mRNA leaves via nuclear pore B1 | 4 |
| (b) | anticodon pairs with codon; carries amino acid tRNA carries a specific amino acid B1 its anticodon pairs with the complementary codon on mRNA B1 amino acids joined by peptide bonds B1 | 3 |
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