Step 1: Definition of Heredity.
The unit of heredity is the gene. A gene is a segment of DNA that carries genetic information for the inheritance of traits. Genes are located on chromosomes and determine characteristics passed from parents to offspring.
Step 2: Conclusion.
Thus, the gene is the basic unit of heredity.
Final Answer:
\[
\boxed{\text{The gene is the unit of heredity.}}
\]