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This wonderful piece of biology starts with the knowledge that some people become allergic to red meat after they have been bitten by a tick. That knowledge sets off a whole bunch of questions and research lines to follow, which then turn up some fascinating learning, covering so many aspects of immunology, biochemistry and even global warming.
READ THIS!!! A SAD STORY ILLUSTRATING BIO-ACCUMULATION
BBC May 2nd 2017
Lulu was found dead in 2016 on the Isle of Tiree in Scotland
This sad story is about the death in 2016 of one of the few remaining killer whales which live off the western coasts of Scotland. Lulu was estimated to be 20 years old and was washed up dead and entangled in fishing net, on a small Scottish island. The cause of her death is not clear but an autopsy discovered unimaginable levels of accumulated PCB chemicals in her body. Polychlorinated biphenyls have been banned since the 1970’s but are so stable that, although slowly reducing in quantities, they are still very present.
PCB’s are synthetic and were widely used in all sorts of ways mid 20th century, but after their toxicity and tendency to bio-accumulate in food chains was better understood, they were banned. Nevertheless PCB’s remain present in the environment and it will be a long time before they vanish.
PCB’s are known to affect reproduction and can damage the immune and nervous systems. The autopsy of Lulu revealed that she probably had never born calves, perhaps because of the high amount of PCB’s in her tissues. It is also quite likely that she suffered brain damage as a result of PCB toxicity.
8 killer whales remain in the pod (group of whales) off western Scotland and one wonders about the PCB levels in their bodies, and whether this bio-accumulation is sadly a major contributing factor to their slow disappearance and projected extinction.
This is a brilliant report, containing links to several parts of the IB Biology syllabus. The few 100 people around the world who suffer from Congenital Insensitivity to Pain (CIP), feel no pain whatsoever. Their sensory pain neurons (nociceptors) are inhibited from generating an action potential by mutation of a gene named SCNP9A, which helps determine the structure of a specific voltage-gated protein channel for sodium (Nav1.7), on the membranes of nociceptors. You might think that inheriting this mutation is good. What better than to not feel pain? You would be very wrong. Many CIP sufferers die early as a result of the damage done to their bodies. This observation in itself is a neat piece of evolutionary natural selection – the CIP condition is so very rare because sufferers do not survive to pass the mutant version of the gene on to their offspring.
The mutation of gene SCNP9A is a missense or point mutation, where just one nucleotide is replaced incorrectly, so leading to mRNA carrying a codon for a different amino acid in translation and protein synthesis.
A spin-off from this research is now a race between different pharmaceutical companies to come up with a magic drug which might somehow work as an anaesthetic in patients suffering extreme pain, by inhibiting the Nav1.7 sodium channels in nociceptors. A new drug of this kind would be very specific to pain neurons and would be a replacement for the billions of painkilling tablets used every year throughout the world.