The process by which DNA codes for proteins in a cell is known as protein synthesis, which occurs in two main stages: transcription and translation.
First, during transcription, the DNA double helix unwinds at the specific region of a gene. An enzyme called RNA polymerase binds to the DNA and synthesizes a single strand of messenger RNA (mRNA) using one of the DNA strands as a template. This mRNA strand carries the genetic information necessary to produce a specific protein.
Once transcription is complete, the mRNA strand leaves the nucleus and enters the cytoplasm. Here, the process of translation takes place. During translation, ribosomes, which are the cellular machinery for protein synthesis, read the sequence of codons in the mRNA. Each codon, a sequence of three nucleotides, corresponds to a specific amino acid.
Transfer RNA (tRNA) molecules bring the appropriate amino acids to the ribosome, matching their anticodon with the mRNA codons. As the ribosome moves along the mRNA, amino acids are linked together in the order dictated by the mRNA sequence, forming a growing polypeptide chain.
Finally, once the ribosome reaches a stop codon, the translation process concludes, and the newly synthesized protein is released to undergo folding and post-translational modifications before it can perform its specific functions in the cell.
In summary, DNA codes for proteins through a precise process involving transcription of DNA into mRNA and translation of mRNA into a specific sequence of amino acids, ultimately resulting in the formation of functional proteins.