From DNA instructions to a protein

By UK A Level Biology · independent study · myAudience

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From DNA instructions to a protein

Transcription produces an RNA copy using a DNA template. In eukaryotes, processing can remove introns and join exons before mature messenger RNA reaches a ribosome. The RNA carries codons, while transfer RNAs bring amino acids using complementary anticodons.

Translation links amino acids in the order specified by the message. A stop codon ends translation rather than adding another amino acid. A supplied code table lets you interpret a short message without memorising every codon.

The proteome describes a cell’s protein repertoire and can change with gene activity, even when its genome remains the same. A DNA template is copied by RNA polymerase into RNA; eukaryotic pre-mRNA is processed before translation. A tRNA carries an amino acid and complementary anticodon, while ATP-dependent steps support the overall synthesis process. Reading AUG–GCU–UAA gives two amino acids because the stop signal ends the chain rather than becoming a third amino acid.

Worked example: A supplied table gives AUG = methionine, GCU = alanine and UAA = stop. Interpret AUG–GCU–UAA.

Read the codons in order.

Add methionine, then alanine.

UAA ends translation.

Answer: A two-amino-acid chain: methionine–alanine.

Check your understanding: What is the role of a tRNA anticodon?

Answer: It pairs with a complementary mRNA codon.

Why: This pairing helps position the corresponding amino acid during translation.