James Priest couldn’t make sense of it. He was examining the DNA of a desperately ill baby, searching for a genetic mutation that threatened to stop her heart. But the results looked as if they had come from two different infants.

“I was just flabbergasted,” said Dr. Priest, a pediatric cardiologist at Stanford University.

The baby, it turned out, carried a mixture of genetically distinct cells, a condition known as mosaicism. Some of her cells carried the deadly mutation, but others did not. They could have belonged to a healthy child.

Continue reading “Every Cell in Your Body Has the Same DNA. Except It Doesn’t.” →

Scientists reported on Wednesday that they have recovered DNA from the oldest viruses known to have infected humans — and have succeeded in resurrecting some of them in the laboratory.

The viruses were all strains of hepatitis B. Two teams of researchers independently discovered its DNA in 15 ancient skeletons, the oldest a farmer who lived 7,000 years ago in what is now Germany.

Until now, the oldest viral DNA ever recovered from human remains was just 450 years old.

Continue reading “In Ancient Skeletons, Scientists Discover a Modern Foe: Hepatitis B” →

The animal kingdom is one of life’s great success stories — a collection of millions of species that swim, burrow, run and fly across the planet. All that diversity, from ladybugs to killer whales, evolved from a common ancestor that likely lived over 650 million years ago.

No one has found a fossil of the ur-animal, so we can’t say for sure what it looked like. But two scientists in Britain have done the next best thing. They’ve reconstructed its genome.

Their study, published in Nature Communications, offers an important clue to how the animal kingdom arose: with an evolutionary burst of new genes.

Continue reading “The Very First Animal Appeared Amid an Explosion of DNA” →