Why did scientists initially believe that proteins were responsible for genetic information?

Scientists initially believed that proteins were responsible for genetic information largely due to the complexity of proteins compared to DNA. Proteins are made up of 20 different amino acids, which can be arranged in a vast array of sequences and structures, leading to the assumption that this complexity could allow proteins to carry the intricate instructions necessary for heredity and trait expression.

In contrast, DNA was seen as a relatively simple structure, composed of only four nucleotides, which made scientists question its ability to encode the complexity needed for genetic information. This perception of simplicity in DNA, coupled with the intricate roles and diverse functions of proteins in cellular processes, led researchers to initially favor proteins as the bearers of genetic information.

Over time, further research revealed the critical role of DNA, particularly with the establishment of its double-helix structure and the understanding of how it serves as a template for RNA synthesis and protein production, ultimately clarifying that DNA holds the genetic blueprint for all living organisms.