Question

Why did scientists originally believe that proteins, rather than DNA, were the molecules that directed protein synthesis?

1) Proteins were the more complex molecules in which genetic information could be stored.
2) Proteins were more likely to have catalytic properties for synthesis reactions.
3) Proteins were the same types of molecules as those that were being synthesized.
4) At the time, more was known about the structure of proteins than that of DNA.

Answer 1

Initially, proteins were thought to be the genetic carriers due to their structural complexity and catalytic properties, but research including Hershey and Chase's experiments later confirmed DNA's role as the genetic material.

Step-by-step explanation:

Scientists originally believed that proteins directed protein synthesis and were the molecules that carried genetic information because they were the more complex molecules with a seemingly endless array of amino acid combinations. This complexity suggested that proteins provided the necessary biological specificity for genetic traits. In contrast, DNA was seen as too simple, as it is composed of only four nucleotides, making it a less likely candidate for storing the vast amount of genetic information needed for an organism's development and function.

Furthermore, enzymes, which are a class of proteins, were well known for their catalytic properties in biochemical reactions, including the synthesis of macromolecules. Given their pivotal role in cellular physiology and the fact that proteins were being continuously synthesized within cells, scientists hypothesized that proteins themselves might encode the biological information necessary for their own synthesis.

It wasn't until the experiments by Hershey and Chase, along with other discoveries related to RNA and mRNA, that the pivotal role of DNA as the genetic material was confirmed. These findings illuminated the true function of DNA as the repository of genetic information and the template from which RNA is constructed, with mRNA carrying the information to ribosomes for protein synthesis.