What are the biochemical units of heredity that make up chromosomes known as?

The correct answer is genes, which are the fundamental units of heredity located on chromosomes. Each gene is a specific sequence of DNA that encodes instructions for building and maintaining an organism's cells and overall functions. Genes carry information that determines physical traits and can influence behavior, development, and susceptibility to disease.

While DNA is indeed the molecule that makes up genes and chromosomes, it is not a unit of heredity in itself. Rather, it is the structural component that genes are made of. Chromosomes are the larger structures that house many genes, and proteins are the end products of gene expression, but they do not themselves determine heredity. Therefore, understanding that genes are the specific segments of DNA responsible for heredity clarifies why this is the correct answer.