Answer: a) a sequence of nucleotides in DNA that codes for a functional product
Explanation: A gene is a segment of a DNA molecule that contains the information required for the synthesis of a functional biological product, whether a protein or RNA.
Genes are transcribed into an mRNA in the process of transcription which is then used for the synthesis of a protein. Not all segments of DNA code for the amino acid sequence of a polypeptide. The coding regions are called the genes while the non-coding regions are called the introns or intervening segments.
