What do chromosomes contain that determines hereditary characteristics?

The correct answer is genes, as they are specific sequences of DNA that encode for traits and characteristics which are passed from parents to offspring. Each gene occupies a specific location on a chromosome and holds the instructions for synthesizing proteins, which play a crucial role in determining an organism's development, functioning, and overall traits.

While DNA itself is the molecule that makes up chromosomes and carries the genetic information, it is the genes contained within that DNA that specifically dictate hereditary characteristics. In simpler terms, genes are the functional units of heredity, and while DNA is the substance that holds those genes, it is the individual genes that convey the inheritance of traits. Thus, understanding the structure and function of genes is essential for grasping how inheritance works in biological organisms.