DNA SEQUENCES:SIMILARITIES BETWEEN chickens and humans are helping scientists find out what controls our cravings for food and alcohol.
Dr Alasdair MacKenzie, from the University of Aberdeen in Scotland, studies Galanin, a gene in humans that causes cravings for food and alcohol. Galanin also regulates mood and feelings of pain.
Using genetic data from a chicken and a collection of other species including dogs and apes and then comparing it with the human genome, Dr MacKenzie isolated the genetic switch that turns Galanin on and off. He also saw that there are two versions of the switch in the human population, which have different effects.
The Galanin gene sits in the middle of a sequence of DNA that does not seem to have a function, so-called “junk DNA”. More and more research is showing however that junk DNA is nothing of the sort. It is likely to be doing all sorts of things that scientists have not yet detected.
This is exactly what Dr MacKenzie found. Presenting his work at the British Science Association festival in Bradford, he showed how he compared the junk DNA sequence around Galanin in humans to DNA sequence from the other animals.
Although on the face of it we don’t look very similar to our feathered relatives, some parts of our genetic code are the same. These matching sequences could have essential roles for life, so essential that they have not changed over the millions of years of evolution separating humans from chickens.
“Conservation suggests importance,” said Dr MacKenzie.
Dr MacKenzie found that a small part of the DNA near the Galanin gene was very similar between humans and all the other animals tested. He looked at what this bit of apparently junk DNA did, and it turned out to be the “on switch” for Galanin, the gene that regulates our appetite.
The Galanin switch is not the same in everyone. There is natural variation in the DNA sequence within the human population, meaning two main types of the switch exists, each with a slightly different DNA sequence, he explained. These two types have different effects – one is better at turning on Galanin than the other.