What’s the News: We’ve long had signs that when it comes to inheritance, DNA isn’t the be-all, end-all. Trees that have the exact same genes but were raised in different greenhouses behave differently. Worms with genes that impart long life can pass on that longevity to their progeny—even if they don’t pass on the genes. Both of these phenomena, we’ve discovered, come from epigenetic changes in tags attached to DNA that control whether genes get expressed.
But every now and then we get a whiff of other possible routes for inheritance, even stranger than that. A new paper in Cell reports that worms whose grandparents had the ability to fight viruses using a fleet of tiny RNA molecules retain these molecules even when they don’t have the genes for them. They can pass these molecules down for more than a hundred generations.
Heliconius numata (top) mimics the wing
pattern of Melinaea mneme (bottom).
What’s the News: A single species of butterfly in the Amazon is able to copy the wing patterns of several neighboring species to avoid being eaten by hungry birds—a wide-ranging talent that has long perplexed evolutionary biologists. Now, an international team of scientists studying the mimicking butterfly Heliconius numata has finally solved this puzzle that plagued even Charles Darwin.
Writing in the journal Nature, researchers found that a specific supergene—a cluster of genes that is passed on to offspring as one big chunk—controls the different elements of wing patterns, allowing related butterflies to display distinct markings despite having the same DNA. “These butterflies are the ‘transformers’ of the insect world,” lead researcher Mathieu Joron said in a prepared statement. “But instead of being able to turn from a car into a robot with the flick of switch, a single genetic switch allows these insects to morph into several different mimetic forms.”
Scientists have now sequenced the genome of the Atlantic cod, revealing something unusual: the cod is missing an important component of the adaptive immune system found in almost all jawed vertebrates. In particular, when the researchers compared the cod’s genome to that of the stickleback (a closely related fish that has already been sequenced), they saw that the Atlantic cod does not have genes that code for the proteins MHC II, CD4, and invariant chain, all of which work together to help the body recognize and fight off invading bacteria and parasites.
Current drugs for conditions from depression to Parkinson’s work by changing levels of chemicals in the brain—an imprecise method that can have a wide range of unintended effects. But a new study suggests it could be possible to make drugs that work by turning off genes instead, getting at, for instance, a specific receptor in a particular part of the brain.
What’s the News: By knocking out a single gene, scientists at the University of Pennsylvania have significantly increased the physical endurance of lab mice, as explained in their recent paper in the Journal of Clinical Investigation. The researchers also found that certain variants of the same gene may be linked to greater endurance in humans.
Dear male reader: Just so you know, your sperm isn’t that different from a sea anemone’s.
Sperm is so vital, a new study in PLoS Genetics found, that one of the genes responsible for it hasn’t changed in 600 million years. Insects, humans, marine invertebrates, other mammals, even fish—the males of all these creatures share a common sperm gene that dates back to before all those animals diverged all those millions of years ago, according to the team led by Eugene Xu.
From an evolutionary point of view, that longevity is simply stunning.
“It’s really surprising because sperm production gets pounded by natural selection,” Xu said. “It tends to change due to strong selective pressures for sperm-specific genes to evolve. There is extra pressure to be a super male to improve reproductive success. This is the one sex-specific element that didn’t change across species. This must be so important that it can’t change” [MSNBC].
Are the racial stereotypes that each of us holds rooted in social fear? That’s the question behind a study out in Current Biology in which researchers investigated children with Williams’ syndrome. This genetic disorder comes from the loss of 26 genes and is marked by, among other things, a lack of social fear in patients: Meeting strangers for the first time, they’ll treat them like old friends.
According to research by Andreas Meyer-Lindenberg and colleagues, those children seemed less given to racial stereotyping than the children without the condition they studied, and the researchers attribute that to the lack of social fear in the kids with Williams’. This result may jibe with previous brain-scanning studies of people with Williams’ syndrome which found unusual activity in their amygdalas, a brain center associated with fear. Interestingly, the children with Williams’ syndrome showed a similar gender bias as the other children, suggesting a different neurological cause for gender and race bias.
However, some scientists point to problems with the study. The sample size is quite small, which is difficult to avoid when studying a rare condition, but still casts doubt on the findings. For instance, 64 percent of the time the children with Williams’ syndrome gave answers that could indicate racial stereotyping, but the margin for error was so large that the researchers concluded 64 percent was not significantly different from 50 percent, a set of perfectly color-blind answers.
For deeper analysis, check out Ed Yong’s post at Not Exactly Rocket Science.
Not Exactly Rocket Science: Williams syndrome children show no racial stereotypes or social fear
80beats: Study: Damage to Brain’s Fear Center Makes People Riskier Gamblers
DISCOVER: How Not To Be a Racist
Image: Current Biology
Researchers from the National Institutes of Health have discovered the first genes linked to stuttering — a complex of three mutated genes that may be responsible for one in every 11 stuttering cases, especially in people of Asian descent [Los Angeles Times]. Scientists have long suspected that stuttering has genetic roots, as it’s often seen in families and twins, but this is the first time they’ve identified genes linked to the problem.
Dennis Drayna, the geneticist who led the study, said he was shocked that two of the implicated genes were linked to rare, fatal metabolic disorders [USA Today], but noted that must stutterers don’t suffer from those disorders. Surprisingly, the genes that were altered in the stutterers are involved in removing metabolic waste from brain cells.