The size of the brain of a chimpanzee (right) is considerably smaller than that of a human brain. Probably multiple stretches of DNA help determine that, geneticists say.
Science Photo Library/Corbis
Being able to insert the two man-made letters into DNA, alongside the usual four-letter alphabet, could teach old cells new tricks and lead to better drugs, researchers say.
courtesy of Synthorx
Botulism bacteria, or Clostridium botulinum, grow in poorly preserved canned foods, especially meat and fish. The microbe's toxin could be lethal as a bioweapon.
Dr. Phil Luton/Science Photo Library/Corbis
This mouse egg (top) is being injected with genetic material from an adult cell to ultimately create an embryo — and, eventually, embryonic stem cells. The process has been difficult to do with human cells.
James King-Holmes/Science Source
The research team used yeast chromosome No. 3 as the model for their biochemical stitchery. Pins and white diamonds in the illustration represent "designer changes" not found in the usual No. 3; yellow stretches represent deletions.
Erick Munoz stands by a photo of his wife, Marlise Munoz, at home in Fort Worth, Texas, on Jan. 3. She is being kept on life support in a local hospital against the family's wishes.
Fort Worth Star-Telegram/MCT via Getty Images
After President Obama overturned Bush-era policy restricting federal funding of embryonic stem cell research in 2009, Nebraska Right to Life led a protest of the research outside the University of Nebraska regents' meeting.