- About the Lecture
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About the Lecture
Sometime around 100 million years ago, when the continents of Africa and South America were still in touch, a female primate -- one of our ancestors -- was born with the capacity to see in vivid color. Jeremy Nathans describes the fortuitous genetic event that gave rise to this evolutionary leap, and links an ancient biological timeline to his very current research in human color vision.
Nathan’s talk, spanning eons and disciplines, starts with Isaac Newton’s astonishing 17th century experiments into the physics of colored light, and his prescient guess that the human brain could somehow translate colors the way it interpreted sound vibrations. The physiology behind vision didn’t coalesce until the 19th century, when a picture emerged of photoreceptor cells, with rods for night vision and cones for color. 20th century science finally cracked the photochemical mechanism behind light sensing.
In the 1980s, Nathans became interested in “making a dent in the area of identifying (genetic) sequences of the visual pigments.” He describes how he isolated the DNA behind the light sensors responsible for human color vision -- the short(S), medium (M) and long (L) wavelength receptors. He also discovered a diversity of genetic variations in normal, trichromatic vision. Indeed, he says the sequences lend themselves to all sorts of “mischief,” which can result in what’s commonly described as color blindness. When genes for the M or L pigments are not expressed, humans lose various degrees of color discrimination. When Nathans shows a picture of fruit from the perspectives of those with normal and abnormal color vision, it’s clear how “trichromats” enjoy an advantage in detecting ripe foods, or just enjoying scenery.
From his genetic research, Nathans became interested in how some mammals made the leap from dichromatic to trichromatic vision. Simple creatures such as honey bees and tropical fish are blessed with better color vision than humans, but among mammals, only a subset of primates have moved to trichromatic vision. Lower mammals lack one of the three dimensions for color vision. Nathans conjectured a “happy accident” on the X chromosome in primates likely resulted in the genes for the additional dimension. In a groundbreaking experiment to “recreate in a mouse the first step in the evolution of trichromatic color vision,” Nathans knocked into the mouse genome a human L pigment gene in place of its M pigment gene, resulting in an animal with the capacity for distinguishing colors a normal mouse could not. “This argues,” concludes Nathans, “that acquisition of a new dimension of color vision is not so difficult after all.”Related Videos
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- About the Speaker
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About the Speaker
Jeremy Nathans '79
Professor of Molecular Biology and Genetics, Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine
Jeremy Nathans is also an investigator at the Howard Hughes Medical Institute. He joined Johns Hopkins and Howard Hughes in 1988. Before that, he received twin B.S. degrees at MIT in Life Sciences and Chemistry, then went on to Stanford University School of Medicine, where he earned both a Ph.D. in Biochemistry and an M.D.
Nathans is a member of the National Academy of Sciences, and the American Academy of Arts and Sciences. He has won the Newcomb-Cleveland Prize from the American Association for the Advancement of Science, and the Initiatives in Research Award from the National Academy of Sciences, among many honors. He is an associate editor of the Journal of Neuroscience and an associate editor of Proceedings of the National Academy of Sciences. Nathans also holds a number of patents for fibroblast growth homologous factors and their methods of use. - About the Host
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About the Host
McGovern Institute for Brain Research at MIT
The McGovern Institute for Brain Research at MIT is led by a team of world-renowned, neuroscientists committed to meeting two great challenges of modern science: understanding how the brain works and discovering new ways to prevent or treat brain disorders. The McGovern Institute was established in 2000 by Patrick J. McGovern and Lore Harp McGovern, who are committed to improving human welfare, communication and understanding through their support for neuroscience research.
Video Player
The Evolution of Trichromatic Color Vision
- Jeremy Nathans '79
- April 27, 2009
- Running Time: 1:07:43
