Unusual DNA Form May Help Virus Withstand Extreme Conditions

A, B and Z DNA.
DNA comes in three forms: A, B and Z. Credit: A-DNA, B-DNA and Z-DNA by Zephyris (Richard Wheeler) under CC BY-SA 3.0.

DNA researcher Rosalind Franklin Exit icon first described an unusual form of DNA called the A-form in the early 1950s (Franklin, who died in 1958, would have turned 95 next month). New research on a heat- and acid-loving virus has revealed surprising information about this DNA form, which is one of three known forms of DNA: A, B and Z.

“Many people have felt that this A-form of DNA is only found in the laboratory under very non-biological conditions, when DNA is dehydrated or dry,” says Edward Egelman Exit icon in a University of Virginia news release Exit icon about the recent study. But considered with earlier studies on bacteria by other researchers, the new findings suggest that the A-form “appears to be a general mechanism in biology for protecting DNA.” Continue reading “Unusual DNA Form May Help Virus Withstand Extreme Conditions”

Delivering Gene-Editing Proteins to Living Cells

Illustration of a DNA strand being cut by a pair of scissors.
Researchers are testing new ways to get gene editing proteins into living cells to potentially modify human genes associated with disease. Credit: Stock image.

Over the last two decades, exciting tools have emerged that allow researchers to cut and paste specific sequences of DNA within living cells, a process called gene editing. These tools, including one adapted from a bacterial defense system called CRISPR, have energized the research community with the possibility of using them to modify human genes associated with disease.

A major barrier to testing medical applications of gene editing has been getting the proteins that do the cutting into the cells of living animals. The main methods used in the laboratory take a roundabout route: Researchers push the DNA templates for making the proteins into cells, and then the cells’ own protein factories produce the editing proteins.

Researchers led by David Liu Exit icon from Harvard University are trying to cut out the middleman, so to speak, by ferrying the editing proteins, not the DNA instructions, directly into cells. In a proof-of-concept study, their system successfully delivered three different types of editing proteins into cells in the inner ears of live mice. Continue reading “Delivering Gene-Editing Proteins to Living Cells”

Neanderthal DNA—Still Among Us

Map of Europe and Asia showing the presumed range of where Neanderthals lived.
For tens of thousands of years, Neanderthals lived in Europe and Asia (presumed range shown in blue) and interbred with humans, passing on some DNA to present-day people. Credit: Ryulong, Wikimedia Commons.
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Many of us have some Neanderthal genes. Before Neanderthals went extinct about 30,000 years ago, they interbred with humans living in Europe and Asia. Today’s descendants of those pairings inherited about 2 percent of their genomes from the big-brained hominids.

A research group led by David Reich at Harvard Medical School recently completed an analysis to determine the extent and identity of Neanderthal DNA in modern-day human populations. The group found that many traits in present-day people—including skin characteristics and susceptibility to various diseases—can be traced to Neanderthal DNA.

It also appears that, genetically speaking, Neanderthals and humans weren’t completely compatible. Based on the uneven distribution of Neanderthal DNA in today’s genomes, the scientists concluded that many of the male offspring of Neanderthal-human unions were infertile. In the animal world, this phenomenon is known as hybrid infertility, where the offspring of a male from one subspecies and a female from another have low or no fertility.

Studying human genes passed down through Neanderthals—as well as regions of the human genome notably devoid of Neanderthal DNA—provides an increasingly complete picture of the genetic landscape that contributed to health, disease and diversity among humans today.

Learn more:
Harvard Medical School News Release Exit icon
Evolution and Health Article from Inside Life Science
Reich Lab Exit icon