How DNA makes proteins
DNA controls the cell (Supplement)
- The base sequence of a gene sets the order of amino acids in a protein.
- A different order folds the protein into a different shape, and the shape decides its job.
- So DNA controls the cell by choosing which proteins (enzymes, carriers, receptors) are made.
- Most cells share the same genes but only express the ones they need.
Practice
The base sequence of a gene sets:
The base sequence determines the amino-acid order, which sets the protein's shape and so its job.
Practice
Most body cells contain the same genes but only express the ones they need.
All body cells share the same genes; each switches on only the genes for its own job.
Making a protein (Supplement)
- A gene stays in the nucleus, but proteins are built in the cytoplasm. mRNA links them:
- mRNA is made in the nucleus as a copy of the gene,
- it moves out to the cytoplasm and into a ribosome,
- the ribosome reads the mRNA bases and joins amino acids in that order.
Practice
Put protein synthesis in order.
mRNA copies the gene → leaves the nucleus → a ribosome reads it → amino acids are joined in order.
You've got it
Key idea
- a gene's base sequence → order of amino acids → protein shape → its job (Supplement)
- cells share genes but only express the ones they need
- mRNA copies the gene; a ribosome reads it to build the protein