Final answer:
A gene is a segment of DNA that directs the synthesis of a specific protein by dictating the order of amino acids in a polypeptide chain. This sequence is translated from the mRNA molecule's nucleotide triplets, called codons, each specifying a particular amino acid.
Step-by-step explanation:
A gene is a segment of DNA that contains the instructions for building a specific protein. The process starts with transcription, where the gene's DNA sequence is copied into messenger RNA (mRNA). During translation, the sequence of nucleotides in mRNA is read in triplets called codons, each corresponding to a specific amino acid. This genetic code determines the sequence in which amino acids are added to the growing polypeptide chain, ultimately folding into a functional protein.
Proteins are essential for various cellular functions, and each protein's unique properties and roles are determined by the specific sequence of amino acids it contains, which in turn is dictated by the gene's nucleotide sequence. The genetic code is universal and is used by almost all organisms to translate gene-encoded instructions into proteins.