A gene is a basic unit of heredity in living organisms. It is made up of DNA and carries the instructions for building and maintaining an organism's cells and passing traits to offspring. Genes determine various characteristics, such as eye color, height, and susceptibility to certain diseases. Genes are organized into structures called chromosomes, which are found in the nucleus of cells. Humans typically have 23 pairs of chromosomes, with each parent contributing one chromosome to each pair. The study of genes and their functions is known as genetics, which helps scientists understand how traits are inherited and how genetic disorders occur.