It’s a key question. How did life on earth come about? The key lies in a simple compound called diamidophosphate (DAP). It is believed that it was already present on our planet before life came into being. It could be responsible for the functional connection of the deoxynucleotides that make up the strands of the first DNA. This is how life could have originated on earth.
The result will be published this week in the journal Angewandte Chemie. The article is called Prebiotic phosphorylation and simultaneous oligomerization of deoxynucleosides to form DNA It suggests the possibility that DNA and its close chemical relative, RNA, formed together as the products of similar chemical reactions. The first life forms on earth emerged from a mixture of the two.
This addresses the age-old question of how life on earth came about. In particular, it paves the way for more extensive studies of how self-replicating mixtures of DNA and RNA (with the ability to make copies of themselves) might have evolved.
“This is an important step in developing a detailed chemical model,” explains lead author of the study, Ramanarayanan Krishnamurthy. He is an Associate Professor of Chemistry at Scripps Research. The finding also raises a chemical alternative to the prevailing “RNA world hypothesis” of the last few decades. He postulates that the first self-replicators were based on RNA and that DNA appeared later.
We now know that modern organisms produce enzymes that can force complementary strands of RNA (or DNA) to separate, making replication easier. But in a world where enzymes didn’t exist, this is a major obstacle. It is difficult to save the RNA world hypothesis.
A chimeric solution
Krishnamurthy argues that “chimeric” molecular chains (part DNA and part RNA) could have solved this problem. Chains would be easier to part with.
DAP may have played the crucial role in modifying ribonucleotides and connecting them to the first strands of RNA. The study shows that DAP could have done the same to DNA under similar conditions. “The DAP reaction with deoxynucleotides works better if they are not all the same,” explains Eddy Jiménez. He is co-author of the study and a research fellow in Krishnamurthy’s laboratory. “An ancient chemistry may have produced the first RNA and DNA molecules. This is how it could have originated on earth, ”adds Krishnamurthy.