Genetics of Primate Evolution
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OVERVIEW
A better understanding of human disease may be gained by taking an evolutionary perspective. For example, why don't our next of kin, the primates, contract the same diseases we do? Analysis of primate physiology provides a window into the evolutionary past of humans in regards to molecular, cellular, and organ function. Humans have not been separated from the great apes for a long time: divergence from a common ancestor from orangutans occurred 13 million years ago (mya), gorillas 8 mya, and chimps only 5-6 mya. Comparative analysis of DNA sequences with these close relatives may allow the elucidation of certain human-specific diseases. Genome-wide comparisons can look broadly at selection across different lineages. Gene-specific comparisons may identify specific disease causing pathways.
Why This Science Matters
The long-held view that traits are encoded as DNA, then transcribed into RNA, and then translated into protein, is changing. Building upon this central dogma of molecular biology is an important area of research called glycobiology. Glycobiology is the study of the structure, chemistry, biosynthesis, and biological functions of sugars and their derivatives. All types of sugar molecules are categorized as carbohydrates or saccharides. Sugars can attach to a protein, for example, without being encoded into the DNA that determines that particular protein. The resulting function of the glycoprotein may be greatly influenced by the type and orientation of the attached sugar. What was once looked upon as "sugar coating" is now understood to have much more influence on the regulation of proteins and the cells of which they are a part.
Cells communicate with the outside world by way of surface sugars called glycans, glycoproteins and glycolipids. One important sugar is sialic acid because it is involved in the first step of the infectious process of many pathogens that cause human diseases. For instance, the invasion of red blood cells by the malaria parasite (Plasmodium sp.) has been shown to be depend on sialic acid binding. However, since chimpanzees do not get malaria, finding out why can lead to a greater understanding of parasitic infections in humans. By comparing evolutionary relationships at the molecular level between humans and our closest relatives it may be possible to describe the origin of human diseases. Also, future research may include genetic modification of sialic acids where the goal is to improve disease prevention.
Many of the similarities between humans and chimpanzees were affirmed with the completion of the Chimpanzee Genome project. Close to thirty percent of proteins found in humans have one hundred percent sequence similarity to the corresponding chimp protein. It was discovered that similar chimp and human proteins show variation in an average of only two amino acids. A very useful database now exists which contains the genetic differences between chimps and humans. This work provides examples of how investigations into the evolution of humans and related primates may elucidate the nature of diseases.
