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Protein synthesis
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Genes are recipes for proteins. Protein synthesis turns the DNA code into a working protein. Separate Biology, Higher.
The genetic code
Three bases (a triplet, or codon) code for one amino acid.
The order of bases in a gene decides the order of amino acids, which decides the protein's shape and function.
The order of bases in a gene decides the order of amino acids, which decides the protein's shape and function.
Transcription
Happens in the nucleus. The DNA unzips and a copy of one gene is made as mRNA (messenger RNA).
mRNA is small enough to leave the nucleus.
mRNA is small enough to leave the nucleus.
Translation
Happens at a ribosome in the cytoplasm. The ribosome reads the mRNA three bases at a time.
tRNA molecules bring the matching amino acids, which are joined into a chain. The chain folds into a protein.
tRNA molecules bring the matching amino acids, which are joined into a chain. The chain folds into a protein.
A gene is 300 bases long. How many amino acids does it code for?
- Three bases code for one amino acid.
- 300 ÷ 3
Answer: 100
A triplet of bases codes for one amino acid. Transcription copies a gene into mRNA in the nucleus. Translation at a ribosome uses tRNA to join amino acids into a protein.
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