Why did people initially believe that proteins carried genetic information rather than DNA?

The belief that proteins carried genetic information rather than DNA stemmed from the perceived complexity of proteins compared to DNA. Scientists observed that proteins, made up of long chains of amino acids, exhibited a vast array of structures and functions, which suggested to them that they could perform the intricate tasks necessary for inheritance and cell function.

In contrast, DNA, composed of only four types of nucleotides, seemed simpler and less variable. This simplicity led some researchers to underestimate its potential role in encoding genetic information. The diverse functions of proteins, including enzymes, hormones, and structural components, further supported the notion that they were responsible for heredity and traits observed in organisms.

As a result, the understanding of molecular biology shifted over time as more evidence emerged, revealing that DNA is the primary carrier of genetic information, ultimately disproving the initial belief regarding proteins.