Final answer:
A gene is the segment of DNA on a chromosome that acts as a blueprint for protein formation and influences an organism's characteristics.
Step-by-step explanation:
The portion of DNA on a chromosome that provides information for an organism's characteristics and serves as the genetic blueprint for the formation of proteins that make up the machinery of the cell is called a gene. Genes are the functional units of heredity, comprising sequences of DNA that code for specific peptides or RNA molecules. Each gene dictates the structure and function of a cell by determining which proteins are made, and thus influences the cell's phenotype, which encompasses all observable characteristics.