People who are unlucky enough to inherit the bad version of both genes have a thirtyfold-higher risk of macular degeneration, says University of Utah geneticist Kang Zhang, who helped nail down the second gene after Yale University researchers first spotted it.

FORBES: Magazine Article

People who are unlucky enough to inherit the bad version of both genes have a thirtyfold higher risk of macular degeneration, says University of Utah geneticist Kang Zhang, who helped nail down the second gene after Yale University researchers first spotted it.

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The second was the introduction of a gene for a synthetic enzyme that he calls aurinase.

ECONOMIST: Genetic engineering

This second gene, activated whenever the gene for P16INK4A was active, produced a protein that was harmless in itself, but which could be made deadly by the presence of a particular drug.

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But if an effect is there, it will always be there unless it is masked by a second, undamaged copy of the gene in question. (There are two versions of most genes in an individual, one inherited from each parent.) That, at least, is the received wisdom.

ECONOMIST: Genetics gets more complicated

And, while rates of obesity dropped substantially between first and second degree relatives of obese patients without the gene mutations, this was far less obvious among relatives of those who were carriers.

BBC: NEWS | Health | Faulty gene link to obesity risk