Biology • Year 12 • Module 5 • Lesson 10
Transcription — From DNA to mRNA
Lock in the core vocabulary, the DNA-template-to-mRNA base-pairing rule, and the reason cells need a temporary mRNA copy of a gene.
1. Term–definition match
The ten definitions below are shuffled. In the right-hand column write the matching term from this list: gene, transcription, mRNA, template strand, codon, uracil, complementary base pairing, nucleus, polypeptide synthesis, hereditary information. 10 marks
| # | Definition (shuffled) | Matching term |
|---|---|---|
| 1.1 | A section of DNA that contains coded base-sequence information for a functional product, usually a polypeptide. | |
| 1.2 | The process of producing an mRNA copy from a DNA template strand. | |
| 1.3 | Messenger RNA — a temporary RNA copy that carries coded information away from a gene. | |
| 1.4 | The DNA strand used as the read-off pattern to build the complementary mRNA sequence. | |
| 1.5 | A three-base sequence on mRNA that carries transferable coded information. | |
| 1.6 | The RNA base that takes the place of thymine and pairs with adenine. | |
| 1.7 | The rule by which A pairs with T (or U in RNA) and C pairs with G during transcription. | |
| 1.8 | The eukaryotic organelle in which the DNA stays during transcription. | |
| 1.9 | The overall process for which transcription is the first step — producing a functional polypeptide from a gene. | |
| 1.10 | Genetic information passed from parent to offspring; the kind of information a gene carries. |
2. True or false — with correction
For each statement, circle T or F. If the statement is false, write the corrected version on the line. 12 marks (1 for T/F, 1 for the correction where needed)
2.1 During transcription, both DNA strands of a gene are copied at the same time into a single mRNA molecule. T / F
2.2 In mRNA, uracil is used in place of thymine, so adenine on the DNA template pairs with uracil on the mRNA. T / F
2.3 The mRNA produced by transcription permanently replaces the original DNA inside the cell. T / F
2.4 A codon is a three-base sequence on mRNA that carries transferable coded information. T / F
2.5 In eukaryotic cells, DNA leaves the nucleus and travels to the ribosome each time a protein is needed. T / F
2.6 Cytosine pairs with guanine during transcription, just as it does in DNA replication. T / F
3. Function recall
Answer each in 1–2 sentences using precise terms from the lesson. 10 marks (2 each)
3.1 What is the function of a gene?
3.2 What is the function of the DNA template strand during transcription?
3.3 What is the function of complementary base pairing in transcription?
3.4 What is the function of mRNA after transcription is complete?
3.5 What is the function of a codon on mRNA at this stage of polypeptide synthesis?
4. Cloze — the transcription paragraph
Fill each blank using one term from the word bank. Words are not all used; some can be used once. 10 marks (1 per blank)
Word bank: gene • template strand • complementary • uracil • thymine • mRNA • codons • nucleus • ribosome • polypeptide synthesis
A (4.1) __________________ is a section of DNA that contains coded base-sequence information for a functional product. To use that information, the cell first carries out transcription: the relevant DNA unwinds and one strand acts as the (4.2) __________________. RNA nucleotides pair with the exposed DNA bases using (4.3) __________________ base pairing, except that RNA contains (4.4) __________________ instead of (4.5) __________________, so adenine on the DNA template pairs with this RNA base. The result is a single-stranded (4.6) __________________ molecule, which is read in three-base units called (4.7) __________________. In eukaryotic cells the DNA remains in the (4.8) __________________, so the mRNA carries the coded information out to be used in the next stage of (4.9) __________________. Without this temporary copy, the cell would have to send DNA itself to the (4.10) __________________ each time a protein was needed.
Q1 — Term–definition matches (10 marks)
1.1 gene • 1.2 transcription • 1.3 mRNA • 1.4 template strand • 1.5 codon • 1.6 uracil • 1.7 complementary base pairing • 1.8 nucleus • 1.9 polypeptide synthesis • 1.10 hereditary information.
1 mark per correct term, max 10.
Q2 — True / false with correction (12 marks)
2.1 False. Correction: transcription uses only one DNA strand of a gene — the template strand — to build the complementary mRNA. The other strand is not copied.
2.2 True.
2.3 False. Correction: mRNA does not replace DNA. It is a temporary, portable copy of the gene's coded information; DNA remains in the nucleus as the original hereditary material.
2.4 True.
2.5 False. Correction: DNA stays in the nucleus in eukaryotic cells. The mRNA produced by transcription carries the coded information out to be used in the next stage of polypeptide synthesis.
2.6 True.
Q3.1 — Function of a gene (2 marks)
A gene's function is to store the coded base-sequence information needed to produce a functional product (usually a polypeptide). The order of bases in the gene determines the order of bases in the mRNA, and ultimately the order of amino acids in the polypeptide.
Q3.2 — Function of the DNA template strand (2 marks)
The template strand acts as the read-off pattern during transcription. Its exposed bases determine, by complementary pairing, which RNA nucleotides are joined together — so the template fixes the mRNA's base sequence.
Q3.3 — Function of complementary base pairing (2 marks)
Complementary base pairing ensures the mRNA sequence faithfully reflects the gene's information. The rules A–U, T–A, C–G, G–C mean that the same template always produces the same mRNA sequence, preserving the coded message.
Q3.4 — Function of mRNA (2 marks)
mRNA acts as a temporary, portable copy of the gene. It carries the coded information out of the nucleus to where it can be used in the next stage of polypeptide synthesis, while leaving the original DNA safely in the nucleus.
Q3.5 — Function of a codon (2 marks)
A codon is a three-base unit on mRNA that holds transferable coded information. Each codon corresponds to specific information that will, in the next lesson, be matched to an amino acid during translation.
Q4 — Cloze answers (10 marks, 1 each)
(4.1) gene; (4.2) template strand; (4.3) complementary; (4.4) uracil; (4.5) thymine; (4.6) mRNA; (4.7) codons; (4.8) nucleus; (4.9) polypeptide synthesis; (4.10) ribosome.