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 hide caption

itoggle caption courtesy of Synthorx

Mary-Claire King says obscurity gave her the freedom to spend years looking for breast cancer genes. Mary Levin/University of Washington hide caption

itoggle caption Mary Levin/University of Washington

Up till now, all babies have had two genetic parents. That could soon change. Klöpper & Eisenschmidt GbR/iStockphoto hide caption

itoggle caption Klöpper & Eisenschmidt GbR/iStockphoto

Research excavations like these in Siberia's Denisova Cave are yielding clues to the mating choices of early hominids. Bence Viola/Nature hide caption

itoggle caption Bence Viola/Nature

This micrograph shows a single mitochondrion (yellow), one of many little energy factories inside a cell. Keith R. Porter/Science Source hide caption

itoggle caption Keith R. Porter/Science Source

Does a glass or two of wine during pregnancy really increase the child's health risks? Epigenetics may help scientists figure that out. Katherine Streeter for NPR hide caption

itoggle caption Katherine Streeter for NPR

Red blood cells are normally shaped like doughnuts, but sickle cells (purple) are flattened and clump together. NIH hide caption

itoggle caption NIH

Bates experienced migraines as a child. She made this painting to depict how they felt to her. Courtesy of Emily Bates hide caption

itoggle caption Courtesy of Emily Bates

A microscopic image of prostate cancer. Researchers have found new genetic markers that flag a person's susceptibility to the disease, as well as breast and ovarian cancer. Otis Brawley /National Cancer Institute hide caption

itoggle caption Otis Brawley /National Cancer Institute

A zygote begins its journey to expression in the form of a human being. Science Picture Co./Science Faction/Getty Images hide caption

itoggle caption Science Picture Co./Science Faction/Getty Images

Kalydeco is one of the first drugs that is effective at combating the root causes of a genetic disease. Vertex Pharmaceuticals Inc. hide caption

itoggle caption Vertex Pharmaceuticals Inc.

A person's DNA can say a lot about a person, but not why someone has committed a horrific crime like mass murder. iStockphoto.com hide caption

itoggle caption iStockphoto.com

When researchers looked at the genetic sequences of 179 individuals, they found far more defects in the patterns of As, Ts, Gs, and Cs than they expected. iStockphoto.com hide caption

itoggle caption iStockphoto.com

A light micrograph image of telomeres, shown in yellow, at the end of human chromosomes. Women tend to have longer telomeres than men and tend to outlive men, according to new research matching genetic information with medical records. Peter Lansdorp/Visuals Unlimited/Corbis hide caption

itoggle caption Peter Lansdorp/Visuals Unlimited/Corbis