RNA and DNA

Fig. 9.12 Formation of a monomolecular layer of a Lipid (After Gilmour and Sephton, 2003)

hydrophilic heads hydrophobic tails hydrophilic heads

- hydrophobic tails hydrophilic heads

Fig. 9.13 Formation of a spherical monocellular layer; the sphere is bathed in water, which surrounds it and isolates a pocket of air within its interior (After Gilmour and Sephton, 2003)

- hydrophobic tails hydrophilic heads

Fig. 9.13 Formation of a spherical monocellular layer; the sphere is bathed in water, which surrounds it and isolates a pocket of air within its interior (After Gilmour and Sephton, 2003)

Following the work of Sydney Altman and Thomas Cech, biologists have come to the conclusion that in the first stage, only RNA was present. In fact, it appears that RNA may carry out some of the enzymatic functions required for replication. In addition, the RNA nucleotides are more easily synthesized than those of DNA. DNA and the proteins necessary for catalysis arose later, DNA having a far more effective replication mechanism than RNA.

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