Genes direct the production of proteins through a process involving two main steps: transcription and translation.
During transcription, the DNA sequence of a gene is copied into a molecule called messenger RNA (mRNA) by RNA polymerase. The mRNA carries the genetic information from the gene to the ribosomes in the cytoplasm, where proteins are synthesized. The mRNA molecule serves as a template for protein synthesis and contains a sequence of nucleotides complementary to the DNA sequence of the gene. This process takes place in the cytoplasm, specifically on ribosomes.
During translation, the mRNA molecule is read by ribosomes, and the genetic information it carries is used to assemble a specific sequence of amino acids. Transfer RNA (tRNA) molecules bring the correct amino acids to the ribosome based on the codons on the mRNA. The ribosome catalyzes the formation of peptide bonds between the amino acids, forming a polypeptide chain. The polypeptide chain then folds into its functional protein structure. Collectively, the processes of transcription and translation are termed gene expression.