What is the relationship between Gene and DNA

a gene is a basic unit of heredity and a sequence of nucleotides in DNA or RNA that encodes the synthesis of a gene product, either RNA or protein.

DNA is a long polymer made from repeating units called nucleotides, each of which is usually symbolized by a single letter: either A, T, C, or G. Chargaff's rules state that DNA from any species of any organism should have a 1:1 protein stoichiometry ratio (base pair rule) of purine and pyrimidine bases (i.e., A+T=G+C) and, more specifically, that the amount of guanine should be equal to cytosine and the amount of adenine should be equal to thymine. The structure of DNA is dynamic along its length, being capable of coiling into tight loops and other shapes