From DNA to Protein
- Biology
- Ages 14–18 · Grades 9–12
What you’ll find out
- Transcription copies a gene into messenger RNA; translation on ribosomes builds the protein it codes for.
- Codons of three bases specify amino acids; transfer RNA delivers them; the folded shape sets the protein’s function.
- Cells control gene expression, so one genome builds many specialised cell types.
No sign-up and no real names. In the lesson you check your understanding as you read, and practise until it sticks.
Transcription and translation
DNA carries the instructions for building proteins, but it stays safely inside the nucleus, while proteins are assembled outside it on tiny structures called ribosomes. The cell solves this by first copying the gene it needs into a similar molecule called messenger RNA, or mRNA, in a process called transcription. The mRNA then leaves the nucleus and attaches to a ribosome. There, the code is read in groups of three bases, called codons, and each codon specifies one amino acid. The ribosome links the amino acids together in the right order, a process called translation. Finally, the chain of amino acids folds into a particular three-dimensional shape, which determines what the protein does.
Controlling which genes are used
Nearly every cell in your body carries the same DNA, yet a nerve cell looks and behaves completely differently from a muscle or skin cell. This is because each type of cell uses, or expresses, only a small selection of its genes, while the rest are kept switched off. Muscle cells express genes for the proteins that make them contract, whereas nerve cells express genes for the proteins that carry electrical signals. Cells can also change which genes they express in response to their surroundings, for instance producing more of certain proteins after exercise or when fighting an infection. Gene expression explains how one genome can build hundreds of different cell types.
Curriculum links: NGSS HS-LS1-1 · England KS4: Biology · Cambridge IGCSE: Biology · NCERT Biology, Class 12