Final answer:
The discovery that genes are composed of nucleic acids can be credited to scientists such as Friedrich Miescher, Richard Altmann, and Albrecht Kossell in the 19th and 20th centuries.
Step-by-step explanation:
The discovery that genes are composed of nucleic acids can be credited to several scientists and their work in the 19th and 20th centuries. In 1869, Friedrich Miescher isolated a compound rich in phosphorus from the nuclei of white blood cells and named it nuclein. His student, Richard Altmann, later discovered its acidic nature and renamed it nucleic acid. Albrecht Kossell characterized the nucleotide bases found within nucleic acids.