Are functional units of heredity that are composed of DNA and specify the structure of proteins.?

Yes, functional units of heredity that are composed of DNA and specify the structure of proteins are called genes. Each gene contains the instructions needed to produce specific proteins, which play crucial roles in the structure and function of an organism. These instructions are encoded in the sequence of nucleotides within the DNA. Genes are fundamental to the processes of inheritance and the expression of traits in living organisms.