Unknowns, From Matter to DNA to Brain Cells

By Valerie Ross|Saturday, January 8, 2011

96  Percent of the universe consisting of unknown components. 23 percent is thought to be made up of poorly understood dark matter, detectable only by its gravitational pull on other material, and 73 percent is dark energy, a completely enigmatic entity that seems to play a role in the accelerating expansion of the universe. Ordinary matter, which makes up the atoms of familiar objects as well as stars and the visible portions of galaxies, accounts for just 4 percent of the cosmos.

12,500  Approximate number of genes in the human genome whose function remains undetermined. These represent about 50 percent of the total estimated number of human protein-encoding genes. And genes make up only about 2 percent of the entire genome. Portions of the remainder help to regulate gene activity, but just how much is useful and how much is truly “junk” remains a mystery. About 3.5 percent of our genome consists of non-protein-coding DNA that we share with mice and rats but whose function is not known.

5 Million  Conservative estimate for the number of undescribed species on the planet; the figure may be as high as 50 million. Only about 1.9 million species have been given scientific names. Vast numbers of bacteria, insects, and creatures of the deep sea remain undescribed. Today’s species are thought to represent less than 1 percent of all species that have ever lived.

85 Billion  Estimated number of cells in the human brain that are not neurons, according to a 2009 study by Brazilian neuroscientists. Neurons make up less than 50 percent of all brain cells. Researchers have only recently begun to catalog the functions of the remaining cells, known as glia. They may supply crucial insulating material for neurons, called myelin; digest and clean up dead cells in the brain; and help form and maintain the connection points between neurons and other cells.

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