The biological term for a segment of a chromosome that controls each characteristic is a gene.

Here's a breakdown:

* Chromosome: A long, thread-like structure made of DNA that carries genetic information.

* Gene: A specific sequence of DNA that codes for a particular trait or characteristic.

* Trait: A specific feature or characteristic of an organism, such as eye color, height, or disease susceptibility.

Therefore, genes are the functional units of heredity, responsible for determining the specific characteristics that an organism inherits from its parents.