The first sign of successful in vitro fertilization, after co-injection of a gene-correcting enzyme and sperm from a donor with a genetic mutation known to cause hypertrophic cardiomyopathy. Courtesy of OHSU hide caption The first sign of successful in vitro fertilization, after co-injection of a gene-correcting enzyme and sperm from a donor with a genetic mutation known to cause hypertrophic cardiomyopathy. Scientists have been tinkering with the DNA in humans and other living things for decades. But one thing has long been considered off-limits: modifying human DNA in any way that could be passed down for generations. Now, an international team of scientists reports they have, for the first time, figured out a way to successfully edit the DNA in human embryos without introducing the harmful mutations that were a problem in previous attempts elsewhere. The work was published online Wednesday in the journal Nature. "It's a pretty exciting piece of science," says George Daley, dean of the Harvard Medical School, who was not involved in the research. "It's a technical tour de force. It's really remarkable." The research is ultimately aimed at helping families plagued by genetic diseases. The new experiment used a powerful new gene-editing technique to correct … Continue reading →

A Mycenaean woman depicted on a fresco at Mycenae on mainland Greece. Yann Forget/Wikimedia Commons By Ann GibbonsAug. 2, 2017 , 1:00 PM Ever since the days of Homer, Greeks have long idealized their Mycenaean ancestors in epic poems and classic tragedies that glorify the exploits of Odysseus, King Agamemnon, and other heroes who went in and out of favor with the Greek gods. Although these Mycenaeans were fictitious, scholars have debated whether todays Greeks descend from the actual Mycenaeans, who created a famous civilization that dominated mainland Greece and the Aegean Sea from about 1600 B.C.E. to 1200 B.C.E., or whether the ancient Mycenaeans simply vanished from the region. Now, ancient DNA suggests that living Greeks are indeed the descendants of Mycenaeans, with only a small proportion of DNA from later migrations to Greece. And the Mycenaeans themselves were closely related to the earlier Minoans, the study reveals, another great civilization that flourished on the island of Crete from 2600 B.C.E. to 1400 B.C.E. (named for the mythical King Minos). The Lion Gate was the main entrance to the Bronze Age citadel of Mycenae, the center of the Mycenaean civilization. RnDmS/iStockphoto The ancient DNA comes from the teeth of … Continue reading →

Molecular model of the lesion that the bacterial toxin yatakemycin forms on DNA. Credit: Elwood Mullins / Vanderbilt One of the most potent toxins known acts by welding the two strands of the famous double helix together in a unique fashion which foils the standard repair mechanisms cells use to protect their DNA. A team of Vanderbilt University researchers have worked out the molecular details that explain how this bacterial toxinyatakemycin (YTM)prevents DNA replication. Their results, described in a paper published online July 24 by Nature Chemical Biology, explain YTM's extraordinary toxicity and could be used to fine-tune the compound's impressive antimicrobial and antifungal properties. YTM is produced by some members of the Streptomyces family of soil bacteria to kill competing strains of bacteria. It belongs to a class of bacterial compounds that are currently being tested for cancer chemotherapy because their toxicity is extremely effective against tumor cells. "In the past, we have thought about DNA repair in terms of protecting DNA against different kinds of chemical insults," said Professor of Biological Sciences Brandt Eichman. "Now, toxins like YTM are forcing us to consider their role as part of the ongoing chemical warfare that exists among bacteria, which can … Continue reading →

Parsing the creatures 2 billion base pairs, Feschotte and his colleagues did stumble on something strange. We found some very weird transposons, he said. Because these oddball parasite sequences didnt appear in other mammals, they were likely to have invaded after bats diverged from other lineages, perhaps picked up from an insect snack some 30 to 40 million years ago. Whats more, they were incredibly active. Probably 20 percent or more of the bats genome is derived from this fairly recent wave of transposons, Feschotte said. It raised a paradox because when we see an explosion of transposon activity, wed predict an increase in size. Instead, the bat genome had shrunk. So we were puzzled. There was only one likely explanation: Bats must have jettisoned a lot of DNA. When Kapusta joined Feschottes lab in 2011, her first project was to find out how much. By comparing transposons in bats and nine other mammals, she could see which pieces many lineages shared. These, she determined, must have come from a common ancestor. Its really like looking at fossils, she said. Researchers had previously assembled a rough reconstruction of the ancient mammalian genome as it might have existed 100 million years … Continue reading →