Octopuses and squid have
confirmed their reputation as Earth-bound aliens with the discovery that they
can edit their own genetic instructions. Unlike other animals, cephalopods –
the family that includes octopuses, squid and cuttlefish – do not obey the
commands of their DNA to the letter. Instead, they sometimes interfere with the
code as it is being carried by a molecular messenger. This has the effect of
diversifying the proteins their cells can produce, leading to some interesting
variations. The system may have produced a special kind of evolution based on
RNA editing rather than DNA mutations and could be responsible for the complex
behaviour and high intelligence seen in cephalopods, some scientists believe. RNA,
a close cousin of DNA, is used to transfer software-like instructions from the
genes to protein-making machinery in cells.
Scientists discovered that more
than 60 per cent of RNA transcripts in the squid brain are re-coded by editing.
In other animals, ranging from fruit flies to humans, such re-coding events
only occur a fraction of 1 per cent of the time. Similar high levels of RNA
editing were identified in three other smart cephalopod species, two octopuses
and one cuttlefish. The mechanics of cephalopod RNA editing are still being
investigated. When do they turn it on, and under what environmental influences?
It could be something as simple as temperature changes or as complicated as
experience, a form of memory. Octopuses and other cephalopods have a number of
characteristics that have caused experts to compare them with aliens, including
instantaneous colour-changing camouflage, blue blood, and an ability to see
polarised light.
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