Four processes were needed for the spontaneous
origin of life on Earth:
1. Non-living synthesis of simple organic molecules
2. Assembly of these molecules into polymers
3. Origin of self replicating molecules that made
inheritance possible
4. Packaging of these molecules into membranes with an
internal chemistry different from their surroundings
In modern living systems, information flows from
WHAT IS RNA?
What is RNA?
• Ribonucleic acid is a nucleic acid
• RNA is essential for all known forms
of life.
• Like DNA, RNA is made up of a long
chain of nucleotides.
Each consists of a base, a
ribose sugar, and a
phosphate group.
How is RNA different than DNA?
• RNA contains the sugar ribose, while DNA
contains the slightly different sugar
deoxyribose
• RNA has the base uracil while DNA contains
thymine.
• Unlike DNA, most RNA molecules are singlestranded and can adopt very complex threedimensional structures.
REMEMBER:
In modern living systems, information flows from
DNA  RNA  Protein
This sequence probably developed in stages
RNA-First Hypothesis
• Through the Wormhole video clip #2
• The first genetic information and enzymes were RNA
molecules
• Why RNA? RNA can act as a catalyst to:
– Bind amino acids together to form proteins
– Replicate itself to create more RNA (animation #1)
• RNA can be
transcribed to DNA
• This could have
given rise to the
first DNA
DNA is more stable
than RNA and
eventually took
over carrying the
genetic
information
Arguments for the RNA First hypothesis
• In Miller’s experiments, ribose was created and
deoxyribose was harder to produce.
• RNA has a simpler structure then DNA.
• RNA exists in viruses (and no DNA)
• It has been proved experimentally that RNA
has catalytic functions (it is a catalyst)
• The DNA-protein system cannot work without
RNA.