Give several pieces of evidence that RNA preceded proteins and DNA in living thi

Question

Give several pieces of evidence that RNA preceded proteins and DNA in living things Do your answers to (1) mean that the first life was RNA-based, with RNA serving as both the catalyst and the genetic material? Briefly discuss the strengths and weaknesses of this hypothesis. It is believed that the machinery for photosynthesis evolved only once, in the cyanobacteria. However, several unrelated groups of eukaryotes, such as green plants, diatoms, and euglenoids, are able to photosynthesize. How can this be explained? Answer each question True or False (T/F). If the answer is false, explain why. Eukaryotic cells are more similar to archaea for genes involved in protein synthesis and DNA replication, but more similar to bacteria for genes involved in metabolism RNA has been found in meteorites, and was produced in the Miller-Urey experiment, giving evidence supporting the "RNA-first" hypothesis of the origin of life. The last universal common ancestor of all living things lived less than 2 billion years ago. The first living things required oxygen (O_2) The^12C/^13 C ratio is higher in living things than in atmospheric CO_2 Which of the following is your closest relative? Your second closest? a) a fungus; b) a dinoflagellate; c) a pine tree; d) a choanoflagellate; e) aciliate; f) an archaean Why are marine organisms relatively common in the fossil record, but mountain-dwelling species relatively rare?

Explanation / Answer

Answer for question 1)

Now a days we know that RNA is coded by DNA and RNA in turn codes for proteins but there is a hypothesis which believes that RNA came first before DNA. According to this hypothesis, RNA stored both genetic information and catalyzed the chemical reactions in primitive cells. Only later due to evolution did DNA take over as the genetic material and proteins become the major catalyst and structural component of cells.

The reasons for this are summarised as :

A) Life perpetuation actually required autocatalysis and this is shown by RNA.

B) RNA as a polynucleotide and polynucleotides can store genetic information as well as catalyze chemical reactions.

C) Single stranded molecule, RNA can assume many conformations which is essential for macromolecular interactions.

Thus because of these reasons, RNA is believed to have preceeded proteins and DNA.

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