What is the basic unit of heredity in living organisms?

The basic unit of heredity in living organisms is a gene. Genes are specific sequences of DNA that encode for proteins or functional RNA molecules and are responsible for the inheritance of traits from parents to offspring. They function as instructions for building and maintaining the body's processes and traits, influencing characteristics such as eye color, blood type, and susceptibility to certain diseases.

While chromosomes, which are structures made of DNA that contain many genes, play a critical role in the organization and distribution of genetic material during cell division, they themselves are not the fundamental units of heredity. Similarly, alleles are different forms of a gene that can exist at a particular locus on a chromosome, representing variations for a trait, but they do not serve as the basic unit of heredity by themselves. DNA is the molecule that contains genetic information and makes up genes but is not considered the smallest functional unit of heredity. Therefore, the concept of a gene precisely defines the hereditary unit responsible for passing genetic information from one generation to the next.