What is Life? 1943
Watson and Crick 1953
The Irish connection
The Central Dogma
The multitude of RNAs
A guide to the Sculpture
Learn about DNA & RNA
?What is life? 2013
The DNA family
THE BOTANIC GARDENS
A photographic guide to the Sculpture |
Where, when and how did life first form? Water is essential for life, and indeed the two are virtually
synonymous. Today it remains one of biology's greatest mysteries, yet RNA, above all other molecules
provides the greatest clue - ?What is life?
Charles Darwin wondered about how life itself first appeared on Earth.
He guessed that there was a phase before cells appeared; in which molecules
evolved in some kind of what today we call a primordial soup. He wrote:-
“But if (and oh what a big if) we could conceive in some warm little pond
with all sorts of ammonia and phosphoric salts, light, heat, electricity
etcetera present, that a protein compound was chemically formed, ready to
undergo still more complex changes…”
As RNA emerges from the warm little pond it rises like three waves up the mound.
Evolution has many twists and turns, successes and failures - whilst we know all RNAs
form in the same way we don't know how they are related and 'underwent still more
RNA The Self-Replicator. Unlike DNA, it catalyzes and replicates, possibly even
itself. Most likely it preceded DNA and, as “The First Multitasker,” it interprets,
regulates and repairs life.
Its twisting forms are as numerous as its known functions.
Several RNAs dance over the crest of the waves. Their names as numerous and fanciful
as our lack of understanding - 'micro', 'hairpin', 'antisense', 'Piwi-interacting', 'small
interfering', 'small nucleolar', 'small temporal', 'sub-genomic' and 'hammerhead'.
No one fully understands the multiplicity of these molecules, which explains
the question-mark shape of the path. But what we do know is that the multifunctional
molecule of RNA is essential to life, and probably the major vehicle in early evolution.
The ascending movement and the words imply there are a few more answers,
and create a rising expectation. Waves become bigger, the phrases longer,
the ascent steeper, the culmination clearer, suggesting a timeline from the
initial question posed by Darwin.
The hammerhead ribozyme is an RNA with the ability to split apart or join
other molecules of RNA at very specific sites, recognised by the sequence of bases.
Discovered in the 1980s, ribozymes (ribonucleic acid enzymes) are capable of
performing specific biochemical reactions, similar to the
action of protein enzymes.
It was so named for the resemblance of molecular diagrams to the T-like shape of a
hammerhead shark. Hammerhead ribozyme RNAs were originally discovered in plant
virus-like RNAs: satellite RNAs and viroids. They have subsequently been
found to be widely dispersed within many forms of life.
The largest and most complex of the ribozymes is the ribosome, the molecule that
translates the mRNA into protein.
This molecule is highly conserved amongst living
things suggesting it is very ancient, and represents a process that may date back 3.7 billion years.
At the top of the mound sits the ribosome molecule next to the transcription seat.
The mRNA is read by the ribosome in sets of three bases at a time. Each codon
corresponds to a specific amino acid. The ribosome brings each amino acid attached
to a transfer RNA (tRNA) into the ribosome-mRNA complex, matching the codon in the
mRNA to the anti-codon in the tRNA, thereby adding the correct amino acid in the
sequence encoding the gene. As the amino acids are linked into the growing peptide
chain, they begin folding into the correct conformation. This folding continues until
the nascent polypeptide chains are released from the ribosome as a mature protein.