85 posts tagged genetics
Tigers need diverse gene pool to survive
Stanford University Original Study
New research shows that increasing genetic diversity among the 3,000 or so tigers left on the planet, though interbreeding and other methods, may be the key to their survival as a species. Iconic symbols of power and beauty, wild tigers may roam only in stories someday soon. Their historical range has been reduced by more than 90 percent. But conservation plans that focus only on increasing numbers and preserving distinct subspecies ignore genetic diversity, according to the study. In fact, following that approach, the tiger could vanish entirely. “Numbers don’t tell the entire story,” says Elizabeth Hadly, professor in environmental biology at Stanford University and senior fellow at the Stanford Woods Institute for the Environment. She is a coauthor of the study, which appears in the Journal of Heredity.
That research shows that the more gene flow there is among tiger populations, the more genetic diversity is maintained and the higher the chances of species survival become. In fact, it might be possible to maintain tiger populations that preserve about 90 percent of genetic diversity. (via Tigers need diverse gene pool to survive | Futurity)
From genetic and genomic testing to new techniques in human assisted reproduction, various technologies are providing parents with more of a say about the children they have and “stirring the pot of ‘designer baby’ concerns,” writes Thomas H. Murray, President Emeritus of The Hastings Center, in a commentary in Science. Murray calls for a national conversation about how much discretion would-be parents should have. “Preventing a lethal disease is one thing; choosing the traits we desire is quite another,” he writes. He discusses public hearings two weeks ago by the United States Food and Drug Administration to consider whether to permit human testing of a new method of assisted reproduction – mitochondrial manipulation – that would prevent the transmission of certain rare diseases and perhaps address some causes of female infertility. At issue is the safety of the technology, as well as its ethical implications. Mitochondrial manipulation creates an embryo with the nuclear DNA from the prospective mother and father (which contains most of the genetic material) and the mitochondrial DNA (containing 37 genes) from a donor without mitochondrial defects. Among the ethical concerns is that daughters produced by this procedure could pass down the mitochondrial DNA to their children. “Up to now, the United States has not allowed such genetic changes across generations,” Murray writes.
Genes predispose obesity but it’s fullness that makes you fat
A genetic predisposition to weight gain and obesity in later life can in part be explained by a lack of feeling full after eating, according to a new study in JAMA Paediatrics. Although there has been some study of why some people appear more likely to gain weight, researchers from UCL and King’s College London were interested in how 28 of the 34 identified “obesity genes” affected children. They found that although someone might be predisposed to becoming obese, it was also due to a tendency to eat more. In other words, predisposition doesn’t mean growing large is inevitable, and recognising it may help avoid overeating. “Our findings suggest that satiety responsiveness [how full we feel after eating] is one of the mechanisms through which obesity genes influence weight,” Clare Llewellyn, research associate in the Health Behaviour Research Centre at UCL and a co-author of the study said. “Obesity genes influence satiety responsiveness, and through influencing satiety responsiveness, they indirectly influence your weight … This study indicated that the reason why some people feel full and other don’t is due to differences in our genes.” The paper is based on the participants to the Twins Early Development Study – a long-term study into more than 16,000 pairs of twins born in the UK between 1994 and 1996. But rather than compare siblings, the researchers chose to study 2,258 participants who weren’t related. The average age of participants was nine. And they used a polygenic (multiple genes) risk score (PRS), which adds up the number of genetic variants someone has that puts them at increased risk of obesity. (via Genes predispose obesity but it’s fullness that makes you fat)
For the first time, scientists at King’s College London have identified a gene linking the thickness of the grey matter in the brain to intelligence. The study is published today in Molecular Psychiatry and may help scientists understand biological mechanisms behind some forms of intellectual impairment. The researchers looked at the cerebral cortex, the outermost layer of the human brain. It is known as ‘grey matter’ and plays a key role in memory, attention, perceptual awareness, thought, language and consciousness. Previous studies have shown that the thickness of the cerebral cortex, or ‘cortical thickness’, closely correlates with intellectual ability, however no genes had yet been identified. An international team of scientists, led by King’s, analysed DNA samples and MRI scans from 1,583 healthy 14 year old teenagers, part of the IMAGEN cohort. The teenagers also underwent a series of tests to determine their verbal and non-verbal intelligence. Dr Sylvane Desrivières, from the MRC Social, Genetic and Developmental Psychiatry Centre at King’s College London’s Institute of Psychiatry and lead author of the study, said: “We wanted to find out how structural differences in the brain relate to differences in intellectual ability. The genetic variation we identified is linked to synaptic plasticity – how neurons communicate. This may help us understand what happens at a neuronal level in certain forms of intellectual impairments, where the ability of the neurons to communicate effectively is somehow compromised.” She adds: “It’s important to point out that intelligence is influenced by many genetic and environmental factors. The gene we identified only explains a tiny proportion of the differences in intellectual ability, so it’s by no means a ‘gene for intelligence’.”
World’s first green piglets born in China, sheep next
In Guangdong Province in Southern China, ten transgenic piglets have been born this year, in and under a black light, they glow a greenish tint. A technique developed by reproductive scientists from the University of Hawai`i at Mānoa’s John A. Burns School of Medicine was used to quadruple the success rate at which plasmids carrying a fluorescent protein from jellyfish DNA were transferred into the embryo of the pig. The green color is a marker that indicates that the fluorescent genetic material injected into the pig embryos has been incorporated into the animal’s natural make-up. The ultimate goal is to introduce beneficial genes into larger animals to create less costly and more efficient medicines. The IBR technique involves proprietary pmgenie-3 plasmids conferring active integration during cytoplasmic injection. This technique was also used to produce the world’s first “glowing green rabbits” in Turkey earlier this year. Turkey is expected to announce results of similar research involving sheep in the New Year. In the video below, the pigs — not unlike human children afraid of the dark — begin to squeal when the lights are turned off, except for the black light, which helps illuminate the green tint. The noise is because the scientists are holding the by-now-large piglets in a container to prevent their movement, to make the florescent glow most visible. (via World’s first green piglets born in China, sheep next | KurzweilAI)
Diabetes risk gene ‘from Neanderthals’
A gene variant that seems to increase the risk of diabetes in Latin Americans appears to have been inherited from Neanderthals, a study suggests.
We now know that modern humans interbred with a population of Neanderthals shortly after leaving Africa 60,000-70,000 years ago. This means that Neanderthal genes are now scattered across the genomes of all non-Africans living today. Details of the study appear in the journal Nature. The gene variant was detected in a large genome-wide association study (GWAS) of more than 8,000 Mexicans and other Latin Americans. The GWAS approach looks at many genes in different individuals, to see whether they are linked with a particular trait. People who carry the higher risk version of the gene are 25% more likely to have diabetes than those who do not, and people who inherited copies from both parents are 50% more likely to have diabetes. The higher risk form of the gene - named SLC16A11 - has been found in up to half of people with recent Native American ancestry, including Latin Americans. (via BBC News - Diabetes risk gene ‘from Neanderthals’)
Phobias may be memories passed down in genes from ancestors
Memories may be passed down through generations in DNA in a process that may be the underlying cause of phobias
Memories can be passed down to later generations through genetic switches that allow offspring to inherit the experience of their ancestors, according to new research that may explain how phobias can develop. Scientists have long assumed that memories and learned experiences built up during a lifetime must be passed on by teaching later generations or through personal experience. However, new research has shown that it is possible for some information to be inherited biologically through chemical changes that occur in DNA. Researchers at the Emory University School of Medicine, in Atlanta, found that mice can pass on learned information about traumatic or stressful experiences – in this case a fear of the smell of cherry blossom – to subsequent generations. The results may help to explain why people suffer from seemingly irrational phobias – it may be based on the inherited experiences of their ancestors. (via Phobias may be memories passed down in genes from ancestors - Telegraph)
Harvey Fineberg: Are we ready for neo-evolution?
Medical ethicist Harvey Fineberg shows us three paths forward for the ever-evolving human species: to stop evolving completely, to evolve naturally — or to control the next steps of human evolution, using genetic modification, to make ourselves smarter, faster, better. Neo-evolution is within our grasp. What will we do with it?
Jealousy: it’s in your genes
The green-eyed monster of jealousy may be hardwired into our DNA, but there is a lot we can do to keep it under control
How would you feel if you suspected your partner had enjoyed a one-night stand while away on holiday without you? What if, instead of having sex on the trip, you believed she or he had fallen in love with someone? In either case, if your partner will probably never see the other person again, would that make the situation any easier to cope with? Faced with either scenario, most of us would feel intensely jealous: it’s a very basic, normal reaction. But does the universality of jealousy indicate that it might be genetically programmed? The first study to investigate the genetic influence on jealousy was recently published. Researchers put the questions at the top of this article to more than 3,000 pairs of Swedish twins. Fraternal twins share about 50% of their genes; identical twins share exactly the same genetic make-up. By comparing the answers given by each group of twins, the researchers were able to show that around one third of the differences in levels of jealousy across the population are likely to be genetic in origin. In both scenarios – fears about a partner sleeping with or falling in love with a stranger – women reported more jealousy than men. But the researchers also found a gender difference between relative reactions to the idea of sexual or emotional betrayal. Men were far more troubled by the thought that a partner had been sexually unfaithful than by potential emotional infidelity. Women tended to respond to each scenario with equal levels of jealousy. Why is this? The answer, according to some scientists, may lie in evolutionary pressures. For both men and women, reproduction is key. But men, unlike women, cannot be certain that they are the biological parent of their child, and so they are naturally more perturbed at the thought of sexual infidelity than they are about emotional infidelity – because it jeopardises the successful transmission of their genes. Women, though relatively less perturbed by the idea that their partner may have been sleeping around, are nevertheless dependent on their mate for their survival and that of their offspring.
Sometime in the not-too-distant future, Marie and Antonio Freeman step into a doctor’s office to design their next child. “Your extracted eggs, Marie, have been fertilized with Antonio’s sperm,” the doctor says. “After screening we’re left with, as you see, two healthy boys and two very healthy girls.” A monitor displays what looks like soap bubbles that bumped into each other on a green background. “Naturally, no critical predispositions to any of the major heritable diseases,” the doctor says. “All that remains is to select the most compatible candidate. We might as well start with gender—have you given it any thought?” “We would want Vincent to have a brother, you know, to play with,” Marie says, referring to her first child. Acknowledging this, the doctor continues: “You have specified hazel eyes, dark hair and fair skin. I have taken the liberty of eradicating any potentially prejudicial conditions: premature baldness, myopia, alcoholism and addictive susceptibility, propensity for violence and obesity—” “We didn’t want—I mean, diseases, yes,” Marie interrupts. “Right, we were wondering if it’s good to leave a few things to chance,” Antonio says. “You want to give your child the best possible start,” the doctor replies. “Believe me, we have enough imperfection built-in already. Your child doesn’t need any additional burdens. And keep in mind, this child is still you, simply the best of you. You could conceive naturally a thousand times and never get such a result.” The Freemans are characters in the science fiction film Gattaca, which explores liberal eugenics as an unintended consequence of certain technologies meant to assist human reproduction. Although Antonio and Marie do not exist outside the movie’s imaginary universe, their real-life counterparts could be walking among us sooner than we think—and, in a sense, they already are.