Question

a gene is described as...
an observable trait
a segment of dna
a type of protein
a change in dna structure

Explanation:

A gene is defined as a functional segment of DNA that contains the instructions to produce a specific molecule (usually a protein or RNA) that contributes to an organism's traits. An observable trait is a phenotype, not a gene. Genes code for proteins but are not proteins themselves. A change in DNA structure is a mutation, not a gene.

Answer:

B. A segment of DNA