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Home Dolphins & Whales Archives Site Map
HUMANS & DOLPHINS: MORE ALIKE THAN PREVIOUSLY THOUGHT
Human genes are helping Texas A&M veterinarians unlock the genetic code of dolphins.
by Mark Evans
Texas Sea Grant
COLLEGE STATION -- Though one eats fish, has fins and glides effortlessly through the water while the other eats hamburgers, wears Reeboks and drives a car to work every morning, humans and dolphins may have more in common than people think, especially when it comes to genetics. In a Sea Grant-funded project, Texas A&M University veterinarians are comparing human chromosomes to those of dolphins and are finding that the two share many similarities. The scientists hope to use these similarities to identify and map the genes of dolphins.
Genes are organized into segments along the length of a chromosome - a tightly wound spool of DNA. This spool is made up of two, complementary, single strands of DNA bound together. Every living thing has a characteristic number of chromosomes, and each chromosome carries different genes. Dolphins have 44 chromosomes, and humans have 46.
Dr. David Busbee and his team applied human "paints," fluorescently labeled pieces of human chromosomes, to dolphin chromosomes on microscope slides. Scientists broke open dolphin cells, releasing chromosomes onto slides. The dolphin chromosomes were then treated with labled human chromosome pieces, providing the opportunity for complementary DNA strands to match up.
...Humans and dolphins may have more in common than people think, especially when it comes to genetics. When scientists examined the photos taken with a fluorescence microscope, they found dolphin chromosomes fluorescently tagged with the labeled, or "painted," pieces of human chromosomes and concluded that dolphins hold many of the same chromosomes as humans. "We started looking at these and it became very obvious to us that every human chromosome had a corollary chromosome in the dolphin," Busbee said. "We've found that the dolphin genome and the human genome basically are the same. It's just that there's a few chromosomal rearrangements that have changed the way the genetic material is put together."
Currently, scientists are trying to determine if the same similarities are true for individual genes on the chromosomes.
For every dolphin chromosome, they are selecting a gene found on the human chromosome and seeing if that same gene shows up in the dolphin at the same place on the chromosome. "We expect to find that a lot of rearrangements have taken place," he said. "We expect there are a number of places where the dolphin genome will reflect differences with the human genome." It is these differences that will tell scientists how long ago dolphins and humans embarked down different branches on the evolutionary tree, he said. According to their genes, Busbee said, dolphins are closely related to cows, antelopes and giraffes, and the domestic pig may be their closest relative.
If scientists can determine the genetic information shared by humans and dolphins, he said, then they may be able to save themselves a lot of time and effort in constructing a genetic map of dolphins. Busbee said they may be able to save as much as 20 years by tapping into all of the work that has been done mapping human genes and using this information to identify matching genes in dolphins. Because of the similar evolutionary history of dolphins and cows, help may also come from Texas A&M University scientists who are constructing a genetic map of the cow.
"Nobody has ever done genetics work on Cetaceans -- whales, dolphins and porpoises," he said "No molecular genetics work has been done with this group before." Once scientists decipher the genetic code of dolphins, Busbee said, they will likely turn their attentions toward uncoding the genes of other members of the whale family. "The chromosome complements between different Cetacean species are pretty close, so if we can apply these data to the dolphin then there's a high degree of likelihood we will be able to apply them to the other cetacean species as well," he said.
The Texas A&M Sea Grant College Program, located at Texas A&M University, collaborates with academic institutions, agencies, and industries throughout the state. The program involves marine-related research, marine advisory service, and communications. The Texas A&M Sea Grant Program supports projects in aquaculture, biotechnology, environmental studies, fisheries, marine education, marine business, seafood sciences and technology, and sociological, economic, legal and policy studies.
Contact: mark-evans@tamu.edu
Texas A&M Sea Grant College Program http://texas-sea-grant.tamu.edu