RNA self replication


** RNA Self Replication **

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** *RNA Self Replication* **

Conceptually RNA should be able to self replicate without the help of
proteins. This is shown in figure 10.1. The original strand serves as a
template. New base pairs arrive and form weak bonds with their complement.
A can form a bond with U, and G can form a bond with C. After one
replication, two complementary strands exist. Another round of replication
is necessary to duplicate the original strand. The complement to the
original strand is also free to make more copies. While this is still the
most promising theory for life's origin, this theory seems to offer more
problems than solutions. This is why the origin of life remains a mystery.

Figure 10.1: Conceptual Model for RNA Self Replication

rna-self-replication.GIF (32635 bytes)

On paper, this model is great. Nevertheless, it does not work all that well
in the lab. The problems were described by Joyce and Orgel as follows:

•    Most strands of RNA are unsuitable templates. The original RNA
molecule that serves as the template must contain a very high concentration
of cytosine to make process 1 in figure 10.1 viable.^2,3 This situation is

Source: www.lifesorigin.com/chap10/RNA-self-replication-3.php

can rna self replicate

RNA world hypothesis - Wikipedia, the free encyclopedia


** RNA world hypothesis **

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For the origin of life, see Abiogenesis.
A comparison of RNA (/left/) with DNA (/right/), showing the helices and
nucleobases each employs.

The *RNA world hypothesis* proposes that self-replicating ribonucleic acid
(RNA) molecules were precursors to current life, which is based on
deoxyribonucleic acid (DNA), RNA and proteins.^[1]^[2] It is generally
accepted that current life on Earth descends from an RNA world,^[3]
although RNA-based life may not have been the first life to exist.^[4]^[5]

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evolution of cellular life.^[6] The RNA world would have eventually been
replaced by the DNA, RNA and protein world of today, likely through an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.^[7] 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.^[5]^[8] The structure of the
ribosome has been called 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

Source: en.wikipedia.org/wiki/RNA_world_hypothesis

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