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Factual: Science & Nature

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A weekly programme looking at the science that's changing our world.

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BBC Inside Science: False positives in genetic test kits, Impact of fishing on ocean sharks, Sex-change fish

False positives in genetic test kits, Impact of fishing on ocean sharks, Sex-change fish

BBC Radio 4 - BBC Inside Science, False positives in genetic test kits, Impact of fishing on ocean sharks, Sex-change fish

False positives in genetic test kits, impact of fishing on sharks, and sex-change species.

There are high numbers of false-positive results produced by the DNA sequencing technologies used by test kits. Plus the impact on sharks by fisheries, and fish that change sex.

Dr Adam Rutherford uncovers the worrying number of false positive results that the DNA sequencing technologies used by 'direct to consumer' genetic test kits are producing. Many of these tests offer analysis on your ancestry, but some also offer to check you out for the likelihood of you being at risk of some genetic diseases like cystic fibrosis or certain types of breast cancer. The tests look for variants in your genome, little changes in your DNA that alter the risk of developing a number of genetic diseases.  The trouble is the rarer the variant, the more likely it is to be disease-causing. But the rarer the variant, the more likely the simple genetic tests are to get it wrong.  And with more and more people sending off their raw genetic data to third-party websites for analysis and annotation, the risk of a false positive result increases to up to 80%. It's a small number of people affected, but a serious one if you're told out of the blue that you are at extreme risk of a serious disease. The advice is to keep an eye on family disease traits and if you are worried, go and see your doctor and get a proper diagnostic test.

Deep sea pelagic sharks, like the great white, silky, tiger, porbeagle and blue are much more vulnerable than their scary reputation suggests. In fact, many shark species are in decline as a result of industrial fishing rapidly encroaching upon their territories, and an increased value of the sharks themselves.  The oceans are big and sharks range far and wide, so understanding these movements is not easy. Professor David Sims, from the Marine Biological Association of the UK and the National Oceanography Centre in Southampton, is part of a huge international consortium of marine biologists who have been tracking 11 species of shark all over the high seas using satellite technology. We’ve been fishing for more than 40,000 years, but our exploitation of the seas got serious in the last 50 years.

In nature, sex can be quite fluid, and in some species, sex changes are just a normal part of every day life. Especially in fish. This type of behaviour is called sequential hermaphroditism, and is common in fish. It's been known about for years, but the underlying genetic mechanisms are mysterious, which is strange for such a radical transformation. In the Blueheaded wrasse, when a dominant male is lost from the shoal, the largest female will immediately begin transforming into a male. Neil Gemmell from the University of Otago in New Zealand has lead a study which for the first time has uncovered the genetics of how the sex change happens.

Producer: Fiona Roberts

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False positives in genetic test kits, Impact of fishing on ocean sharks, Sex-change fish

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