Tuesday, May 19, 2009

Many paths to a single trait

Ironically, there's a story today on the BBC website about an Australian ostrich farmer who needed emergency care for lung paralysis after drinking 4-6 liters of cola a day for some time. And, a woman who had an irregular heartbeat and extreme fatigue after drinking up to 3 liters of cola per day. The investigators warn that heavy cola consumption, because of its high sugar and caffeine content, could cause hypokalemic muscle paralysis (paralysis induced by low potassium) in anyone.

This response to sugar sounds very much like what we described in our post on single gene disorders on May 15. Does this mean that someone like the ostrich farmer actually has a mild form of hkpp, with a corresponding gene mutation, or are all of us at risk, given enough sugar or salt or other trigger, no matter our genotype?

Well, anyone whose potassium drops enough to affect the workings of their ion channels would respond similarly, thus anyone who consumes enough sugar to cause a drop in their potassium levels could experience this kind of weakness or paralysis. People with hkpp just happen to reach hypokalemic levels more easily, because of the inability of their ion channels to allow cells to release potassium as they should.

There are often many ways to a given trait, both genetically and behaviorally, and this trait appears to be the same. Like most traits, it appears to be multifactorial, or even polygenic, with a few factors such as some key gene mutations or specific environmental overloads producing disease, while it may be that most of us manifest some symptoms under some conditions: a spectrum of cause and effects.

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