Question

Biologists believe that the current DNA $\to$ RNA $\to$ Protein system is the result of a long period of evolution because

• A. The transcription of DNA to mRNA and translation of mRNA into proteins consists of many steps.
• B. DNA replication is complicated but relatively error-free and the current system is very complex and precise.
• C. Evidence indicates that RNA preceded DNA as the genetic material.
• D. All of the above.

Answer 1

Answer: (C)

Evidence indicates that RNA preceded DNA as the genetic material.

The RNA world hypothesis proposes that self-replicating ribonucleic acid (RNA) molecules were precursors to all current life on Earth. It is generally accepted that current life on Earth descends from an RNA world, although RNA-based life may not have been the first life to exist.
RNA stores genetic information like DNA, and catalyzes chemical reactions like an enzyme protein. It may, therefore, have played a major step in the evolution of cellular life. The RNA world would have eventually been replaced by the DNA, RNA and protein world of today, likely through an intermediate stage of ribonucleoprotein enzymes such as the ribosome and ribozymes, since proteins large enough to self-fold and have useful activities would only have come about after RNA was available to catalyze peptide ligation or amino acid polymerization. DNA is thought to have taken over the role of data storage due to its increased stability, while proteins, through a greater variety of monomers (amino acids), replaced RNA's role in specialized biocatalysis.
The RNA world hypothesis is supported by many independent lines of evidence, such as the observations that RNA is central to the translation process and that small RNAs can catalyze all of the chemical group and information transfers required for life. The structure of the ribosome has been called as the "smoking gun," as it showed that the ribosome is a ribozyme, with a central core of RNA and no amino acid side chains within 18 angstroms of the active site where peptide bond formation is catalyzed.
So, Most biologists think that RNA was the first genetic material because, the existence of ribozymes suggests that early cells could have used RNA to catalyze chemical reactions and transfer information. So, Biologists believe that the current DNA RNA protein system is the result of a long period of evolution because evidence indicates that RNA preceded DNA as the genetic material. Thus, option C is correct and other options are wrong.