TranscriptionTranscriptionMaking an RNA copy of a gene from a DNA template., translationTranslationAssembly of a protein at the ribosome using mRNA as instructions., and the genetic codeGenetic codeThe set of rules mapping each mRNA codon to a specific amino acid or stop signal. It is nearly universal across life.: how sequence becomes function. Module 2.
Recap: the central dogma
Genetic information, the instructions encoded in DNADNADouble-stranded molecule storing genetic information as A, T, G, C bases., generally flows in one main direction, from DNADNADouble-stranded molecule storing genetic information as A, T, G, C bases. to RNARNARibonucleic acid: usually single-stranded nucleic acid that uses uracil (U) instead of thymine (T). mRNA carries the protein-coding message from DNA. to proteinProteinA folded chain of amino acids that performs a specific function in the cell.. First, DNADNADouble-stranded molecule storing genetic information as A, T, G, C bases. stores the long-term instructions in the nucleus (the cell's control center). The first step, transcriptionTranscriptionMaking an RNA copy of a gene from a DNA template. (copying a geneGeneA stretch of DNA that codes for a functional product, usually a protein. into RNARNARibonucleic acid: usually single-stranded nucleic acid that uses uracil (U) instead of thymine (T). mRNA carries the protein-coding message from DNA.), creates a messenger RNAmRNAMessenger RNA: carries a gene's code from nucleus to ribosome. (mRNAmRNAMessenger RNA: carries a gene's code from nucleus to ribosome.) copy. That working copy can leave the nucleus and reach the machinery that builds proteinsProteinA folded chain of amino acids that performs a specific function in the cell.. Then translationTranslationAssembly of a protein at the ribosome using mRNA as instructions. reads mRNAmRNAMessenger RNA: carries a gene's code from nucleus to ribosome. in 3-base units called codonsCodonThree nucleotides in mRNA that code for one amino acid or a stop signal.. Each codonCodonThree nucleotides in mRNA that code for one amino acid or a stop signal. tells the cell which amino acidAmino acidMonomer with an amino group, carboxyl group, and unique side chain. to add next: a small building block that links into a proteinProteinA folded chain of amino acids that performs a specific function in the cell. chain. The cell links those amino acidsAmino acidMonomer with an amino group, carboxyl group, and unique side chain. into a chain, a proteinProteinA folded chain of amino acids that performs a specific function in the cell.. Think of it this way: DNADNADouble-stranded molecule storing genetic information as A, T, G, C bases. is the archive. RNARNARibonucleic acid: usually single-stranded nucleic acid that uses uracil (U) instead of thymine (T). mRNA carries the protein-coding message from DNA. is the working copy. The proteinProteinA folded chain of amino acids that performs a specific function in the cell. is the molecule that actually does the job.
Before cell division, the double helix unzips and each strand serves as a template for building a new complementary strand, producing two identical DNA molecules.
RNA polymerase binds to the gene's promoter and reads the DNA template strand, building a complementary mRNA molecule that then travels out of the nucleus.
The ribosome reads mRNA codons (triplets). Each codon is matched by a tRNA carrying the corresponding amino acid. Peptide bonds link the amino acids into a growing polypeptide chain.
After translation, proteins fold into a 3D shape that determines their function — as enzymes, structural components, signalling molecules, or transporters. Amino acid sequence dictates the shape.
