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Human to Pig Genome Comparison Complete

Published August 8, 2005
URBANA - Another mystery of life has been unraveled, one DNA strand at a time. University of Illinois animal geneticists Lawrence Schook and Jonathan Beever have created a side-by-side comparison of the human genome and the pig genome that reveals remarkable similarities. "We took the human genome, cut it into 173 puzzle pieces and rearranged it to make a pig," said Schook. "Everything matches up perfectly. The pig is genetically very close to humans."

Schook explained that when we look at a pig or a human, we can see the difference instantly. "But, in the biological sense, animals aren't that much different from one another -- at least not as different as they appear," he said. Animals all have eyes, ears, stomachs, etc., but as Beever put it, "The same gene in the pig may work in combination with other genes to control something very different than it does in a human."

So, if all of the genes match up, what is it that makes a pig a pig and a human a human? "That's the million dollar question," said Beever. "The genes match up when compared side-by-side, but understanding how they work together is the next step."

A genome is the complete set of genes for an organism -- like an instruction manual, but in this manual, the steps aren't in any particular order. Beever explained, "We don't know, for instance, when in the development of the animal a certain gene is expressed. And the same gene may behave very differently in a different animal. That's the next level of information we'll be looking at."

Why do we need this much information about the pig? "It's clear that the pig one of the closest large animal species to humans," said Beever. "We believe a niche the pig has will be in biomedical models to understand and fight human disease. If you study a human genetic disease in a lab mouse, the manifestations of the disease may not be appropriate. But genetic diseases may look the same in a pig as it does in a human, so disease research with pigs will be much more applicable to human medicine," said Beever.

Schook said that the pig genome map will be very beneficial for use with drug therapy to control or cure a disease. "If you're looking at simple toxicity, whether a disease will kill you, then using a mouse is fine. But when looking at drug therapy, it isn't comparable to humans. Therapeutic medicine requires a more closely related model," he said.

For example, Schook and Beever are looking at a gene that predisposes a person to develop plaque that can cause cardiovascular disease. "Having both the human and the pig genomes, we can look at the genetic variations in the human genome that contributes to the disease and compare it to the same sequence in the pig," said Schook. "Then we can do specific and focused research."

Interestingly, Beever pointed to one spot on the color print out of the pig genome and identified it as the one chromosome that is completely conserved in all mammals. Perhaps someday the mystery of why it has been conserved over such a broad evolutionary range will also be unraveled.

Part one of the project, which is scheduled to be published in Animal Genetics, was sequencing approximately 1% of the genome of the pig. Part two, which will be published in an upcoming issue of Genomics, is the comparative work. Schook and Beever along with other U of I researchers are in the third year of a five-year study funded by the USDA to create comprehensive genome maps of the pig and the cow.

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