The segment of DNA that contains the information necessary to express inherited traits in an organism is called a gene.

Here's a breakdown:

* Gene: A specific sequence of DNA that codes for a particular protein or functional RNA molecule.

* Protein: Proteins are the workhorses of the cell, performing a wide variety of functions, from structural support to enzymatic activity.

* Inherited Traits: These are characteristics that are passed down from parents to offspring, such as eye color, hair color, or susceptibility to certain diseases.

How it works:

1. Transcription: The DNA sequence of a gene is copied into a messenger RNA (mRNA) molecule.

2. Translation: The mRNA molecule is used as a template to assemble a specific protein.

3. Protein Function: The protein then performs its designated function, contributing to the organism's traits.

So, genes are the fundamental units of heredity, containing the blueprints for building and maintaining an organism.