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> For starters, LUCA may not have used DNA. Poole has studied the history of enzymes called ribonucleotide reductases, which create the building blocks of DNA,

• KMag 12y ago
  In order to produce the proteins encoded in DNA, cells first make messenger RNA (mRNA) copies of the information in the DNA and then the rhibosomes translate the mRNA into amino acid sequences. So, while DNA is much more stable than RNA, it's not obvious that an organism couldn't just get rid of DNA, work with RNA, and deal with a higher mutation and degredation rate. Plenty of viruses use only RNA to carry their genetic material. There's a long-standing debate over whether enzymes or nucleic acids came first. In modern cells, enzymes are necessary to catalyze energy-producing reactions and other chemical reactions, and nucleic acids are necessary to store the information necessary for self-replication. It seems unlikely that nucleic acids and enzymes both were randomly spontaneously generated and worked together in the first self-replicating chemical reactions. Instead, most people have theorized that either early cells used proteins to store information or used nucleic acids to catalyze reactions. It has been shown in the lab that some reactions can be catalyzed by RNA. So, the theory goes something like (1) self-replicating RNA spontaneously arises that both catalyzes reactions and carries information (2) mutations in some of the RNA causes it to create enzymes, which make much better catalysts and out-compete RNA-only life (3) RNA-enzyme life mutates and starts using DNA as a more stable storage format than RNA, making those DNA-RNA-enzyme organisms more robust and these out-competed all RNA-enzyme organisms.