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All 12 Flashcards — Transcription: making mRNA
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Question
What is transcription?
Answer
The copying of a gene's DNA base sequence into a complementary molecule of **mRNA**. It happens in the **nucleus**.
Question
Which enzyme carries out transcription?
Answer
**RNA polymerase** — it unwinds the DNA and joins RNA nucleotides into mRNA.
Question
Where does transcription take place?
Answer
In the **nucleus** (where the DNA is).
Question
What is mRNA?
Answer
A single-stranded copy of a gene that carries its base sequence **out of the nucleus to a ribosome** to be translated.
Question
How many DNA strands are copied during transcription?
Answer
**One** — only the **template strand** is read and copied.
Question
In mRNA, which base pairs with adenine (A) on the DNA template?
Answer
**Uracil (U)** — RNA has no thymine.
Question
What are the base-pairing rules in transcription?
Answer
Template **A → U**, template **T → A**, template **C → G**, template **G → C**.
Question
Why does mRNA use uracil instead of thymine?
Answer
RNA contains **uracil (U)** in place of thymine; so a template adenine is copied as **U**, never T.
Question
Why is mRNA important in protein synthesis?
Answer
It **carries the gene's code out of the nucleus to a ribosome**, where it is translated into a polypeptide.
Question
What does RNA polymerase do, step by step?
Answer
Binds the gene, **unwinds** the DNA, reads **one template strand**, pairs and **joins free RNA nucleotides** into mRNA.
Question
Match the enzymes: which makes mRNA and which copies DNA?
Answer
**RNA polymerase** → transcription (mRNA); **DNA polymerase** → DNA replication.
Question
A drug blocks RNA polymerase. What happens to protein synthesis?
Answer
**No mRNA is made**, so there is nothing for the ribosome to translate — the protein cannot be built.
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Topic 4.2 hub
Protein synthesis
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