Agence France-Presse PARIS -- Men significantly outnumbered women in the "out-of-Africa" migration some 60,000 years ago that eventually populated the rest of the world, according to a new study. Africa is known to be the cradle of human evolution, and recent studies show that the people inhabiting other continents originate from a relatively small band of Homo sapiens who moved through the Near East, into Europe and beyond some 50,000 and 70,000 years ago. But until now no one had figured out a way to determine what the sex-ratio of this so-called founding population might have been. A quartet of researchers led by Alon Keinan at the Harvard Medical School thought that the secret might be locked inside differences in genetic code across distinct geographic regions. They knew that the percentage of X chromosomes in a given population varies depending on the proportion of men. The "X" and "Y" chromosomes determine sex -- men have one of each, while women have two X chromosomes. The other 22 chromosome pairings in the human genome are all the same. It was also known that this ratio affects the rate at which mutations randomly spread through the X chromosome over dozens or hundreds of generations as compared to the mutation rate in other, non-sex, chromosomes. Keinan and colleagues reasoned that if X-chromosomes changed more quickly than expected, then it almost certainly meant that our common ancestors who wandered out of Africa were predominantly male. To test their theory, they compared the genetic makeup of Africans first with northern Europeans, and then again with Asians. "The results point to a period of accelerated drift on chromosome X that largely occurred after the split of West Africa and non-Africans, but before the separation of North Europeans and East Asian," the conclude. Genetic drift is a term that refers to random mutations in genes, as opposed to changes that occur through natural selection. Keinan acknowledged that if a small fraction of the women in the migratory exodus from Africa had given birth to all of the children, there might still have been parity in the number of males and females. But this seemed highly unlikely, he said, adding that his findings were "in line with what anthropologists have taught us about hunter-gatherer populations in which short distance migration is primarily by women and long distance migration primarily by men." The study was published in Nature Publishing Group's journal Nature Genetics.
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By Agence France-Presse CHICAGO -- Scientists have discovered a more efficient way of building a synthetic genome that could one day enable them to create artificial life, according to a study released Wednesday. The method is already being used to help develop next generation biofuels and biochemicals in the labs of controversial celebrity US scientist Craig Venter. Venter has hailed artificial life forms as a potential remedy to illness and global warming, but the prospect is highly controversial and arouses heated debate over its potential ramifications and the ethics of engineering artificial life. Artificially engineered life is one of the Holy Grails of science, but also stirs deep fears as foreseen in Aldous Huxley's 1932 novel "Brave New World" in which natural human reproduction is eschewed in favor of babies grown in laboratories. The J. Craig Venter Institute succeeded in synthetically reproducing the DNA of a simple bacteria last year. The researchers had initially used the bacteria e. coli to build the genome, but found it was a tedious, multi-stage process and that e. coli had difficulty reproducing large DNA segments. They eventually tried using a type of yeast called Saccharomyces cerevisiae. This enabled them to finish creating the synthetic genome using a method called homologous recombination, a process that cells naturally use to repair damage to their chromosomes. They then began to explore the capacity for DNA assembly in yeast, which turned out to be a "genetic factory," the Institute said in a statement Wednesday. The researchers inserted relatively short segments of DNA fragments into yeast cells through homologous recombination method. They found they were able to build the entire genome in one step, according to the study set to be published in the Proceedings of the National Academy of Sciences. "We continue to be amazed by the capacity of yeast to simultaneously take up so many DNA pieces and assemble them into genome-size molecules," said lead author Daniel Gibson. "This capacity begs to be further explored and extended and will help accelerate progress in applications of synthetic genomics." Senior author Clyde Hutchison added, "I am astounded by our team's progress in assembling large DNA molecules. It remains to be seen how far we can push this yeast assembly platform but the team is hard at work exploring these methods as we work to boot up the synthetic chromosome." Venter and his team continue to work towards creating a living bacterial cell using the synthetic genome sequence of the Mycoplasma genitalium bacteria. The bacteria, which causes certain sexually transmitted diseases, has one of the least complex DNA structures of any life form, composed of just 580 genes. In contrast, the human genome has some 30,000. Using the genetic sequence of this bacteria, the Maryland-based team has created a chromosome known as Mycoplasma laboratorium. They are working on developing a way to transplant this chromosome into a living cell and stimulate it to take control and effectively become a new life form.
By Izah Morales INQUIRER.net CEBU, Philippines – Scientists today are using genetic engineering to improve the short shelf-life and post-harvest losses of papaya and lessen use of pesticides on eggplants, experts said during a symposium on biotechnology and nutritionally enhanced food crops here. According to Dr. Evelyn Mae Tecson-Mendoza, research professor of Biochemistry at the Institute of Plant Breeding-University of the Philippines Los Banos (IPB-UPLB), the transgenic papaya or genetically modified papaya by recombinant has now longer shelf-life than the ordinary papaya. "The papaya usually ripens two days after having a full yellow color and you have to eat it on the second or the third day. Otherwise, it won't be edible. With this technology, we can delay it from 4 up to 14 days," elaborated Mendoza. Delaying the ripening of papaya was made possible through suppressing the production of ethylene. This was done by inhibiting the ACC synthase from synthesizing through the antisense technology, Mendoza said. Since 1997, Mendoza has been using molecular techniques to solve the problem on post-harvest losses measuring from 30 to 40 percent and the shelf-life of the papaya. But it was only after 10 years that they conducted the first field testing of a homegrown papaya. Based on the results of the various biochemical testing, Mendoza said the nutritional value of the transgenic papaya is similar to the ordinary papaya noting that both have Vitamin C and antinutrient benzyl isothiocyanate (BITC) contents. Dr. Frank Shotkoski, director of the Agricultural Biotechnology Support Project II Cornell University, for his part, related that the nutritional values of Bt eggplant and the ordinary eggplant are identical. Both Shotkoski and Mendoza are optimistic about the eventual transfer of the technology to farmers. Shotkoski cited that farmers in India have a high demand for the Bt eggplant. Mendoza disclosed that it will take two years before farmers in the Philippines can use the technology. "Because this is a technology that involves recombinant DNA technologies and there are biosafety regulations. We need to do field testing under biosafety regulations and we're also into progression of incorporating the PRSV (papaya ringspot virus) resistance," explained Mendoza. Meanwhile, Shotkoski deemed it important to analyze the socio-economic impact and risk assessment of the technology. "We don't want to spend an enormous amount of national public money on a project that has very little or no return on investment. If we plan to spend $2 to 3M on a project and it won't have any benefit to the consumer or the farmer, then the technology won't be adapted. We use this as a guide to assess the probability or the likelihood whether the technology would be adapted," said Shotkoski.
By Izah Morales INQUIRER.net CEBU, Philippines -- Among the member countries of the Association of Southeast Asian Nations (ASEAN), the Philippines is the most advanced in implementing safety regulations for genetically modified (GM) crops, experts said here. "Pinaka-advance tayo kasi we were able to commercialize GM products such as Bt (Bacillus thuringiensis) corn and herbicide-resistant corn. [We are the most advanced because we were able to commercialize genetically modified products such as Bt corn and herbicide-resistant corn.]," said Reynaldo Ebora, executive director of the Philippine Council for Advance Science and Technology Research and Development (PCASTRD) of the Department of Science and Technology (DOST). In contrast, LAO PDR and Myanmar are still in the initial stages of developing biosafety policies. Biosafety laws in Cambodia and Malaysia were approved in January 2008 and July 2007, respectively. Meanwhile, Indonesia, Thailand and Vietnam that have existing regulations are conducting field trials, said Ebora during a symposium on Biotechnology and Nutritionally Enhanced Food and Crops here in Cebu. Ebora pointed out that market acceptance of GM crops is not a problem in the Philippines. "Kasi ang mga farmer, mas gusto nila dahil mas mataas ang yield. Sa general public, it seems na mataas ang public acceptance. Kasi kung hindi mataas ang public acceptance, kakaunti sana ung bibili ng seeds na itatanim.Ang problema ngaun, kulang ung seeds na itatanim. [The farmers wanted Bt corn because it has higher yield. It also seems that the public acceptance is high. If the public acceptance is not high, then only few would buy seeds for planting. But the problem now is that there are few seeds.]," Ebora said. Safety regulations GM crops can bring back trust in them, added Dr. Junshi Chen of the Chinese Center for Disease Control. "The Chinese government has decided to give a larger amount of financial investment to further study new GMOs for the Chinese population. It is serious on safety evaluation and safety assessment of new products," Chen said.
By Agence France-Presse PARIS -- Scientists have grown genetically engineered purple tomatoes in an unusual endeavor to promote healthy food. The tomatoes include two genes taken from the snapdragon flower (Antirrhinum majus) to enable them to express a compound called anthocyanin, the purple pigment found in high levels in fruit such as blackberries and cranberries. Previous research has found that anthocyanins offer protection against certain cancers, cardiovascular disease and degenerative diseases, and may also hinder inflammation, obesity and diabetes. The study is published online on Sunday by Nature Biotechnology, a journal of the London-based Nature Publishing Group. Researcher Cathie Martin from the John Innes Centre, a biotechnology institute in Norwich, eastern England, said the point behind the purple toms was to boost the healthiness of diets. More than 20 years ago, the National Cancer Institute of America initiated a "five-a-day" programme to encourage Americans to consume at least five portions of fruit and vegetables daily. But the numbers of Americans achieving this goal has declined over the last 10 years. Less than one in four reach the "five-a-day" target. The failure of awareness campaigns has shifted the balance in favour of food with higher levels of healthy compounds, especially in ingredients that people eat in large amounts, argued Martin. "Most people do not eat five portions of fruits and vegetables a day, but they can get more benefit from those they do eat if common fruit and veg can be developed that are higher in bioactive compounds," she said. After creating the purple tomatoes in a lab, the team tested the products on mice that they had engineered to make them susceptible to cancer. Mice fed with the high-anthocyanin tomatoes "showed a significant extension" of lifespan, they found. "This is one of the first examples of metabolic engineering that offers the potential to promote health through diet by reducing the impact of chronic disease, and certainly the first example of a GMO [genetically-modified organism] that really offers a potential benefit for all consumers," Martin said. "The next step will be to take the preclinical data forward to human studies with volunteers to see if we can promote health through dietary preventive medicine strategies." Genetically-modified food has focused mainly on gene changes that offer advantages to farmers. Examples include corn that exudes a natural toxin to kill insect pests, and rapeseed, also called canola, that resists a pesticide, thus enabling the farmer to spray his entire field in one go, killing weeds but not the crops. There have also been other schemes to boost the healthiness of food, such as "golden rice" and genetically-modified bananas that included inserted genes to increase levels of vitamin A. But none is commercially available for human consumption. Opponents say food deficiencies are linked to poverty and other social issues that cannot be resolved by gene technology. They also contend that genetic modification may have impacts for human health and the environment. Most experts say the evidence for this so far is zero or negligible.
By Agence France-Presse PARIS--Scientists on Sunday announced they had uncovered the first gene that helps explain common differences in height among humans. Just a single change in the gene's DNA code determines whether people will be taller or shorter by up to one centimeter (0.4 of an inch), they said, adding that hundreds of other genes are also likely to play a role in height. Genetic heritage has long been known as the driver of height -- everyone knows that a child whose parents are both tall is also likely to grow up tall, too. Unlike obesity, where genes and environmental factors (nutrition and exercise for example) play a joint role, around 90 percent of the determinants for height are genetic. Even though the link is clearly there, finding "height" genes that are common across the population has been strangely elusive. Until now, the only evidence has been spotted among a small group of people with a rare condition that affects their stature. In a paper published by the journal Nature Genetics, British and US sleuths analyzed DNA from nearly 5,000 white people of European descent, mainly individuals living in Britain, Sweden and Finland. The exhaustive trawl threw up a gene called HMGA2. The change of just a single base "letter" in HMGA2's genetic code -- a "C" (for cytosine) instead of a "T" (for thymine) -- adds nearly a centimeter (0.4 of an inch) in height to individuals who inherited this variant from both parents. Those who got the "C" variant from only one of their parents were about half a centimeter (0.2 of an inch) taller than their "T" counterparts. After comparing this discovery to further studies of nearly 30,000 other people, the team believes around a quarter of white Europeans carry the double "C" variant. Around a quarter have the double "T" version, thus leaving them about a centimeter (0.4 inch) shorter than their double "C" counterparts. Many more other genes remain to be uncovered, for HMGA2 explains only 0.3 percent of the variability in human stature. "Height is a typical 'polygenic' trait, in other words many genes contribute towards making us taller or shorter," said lead researcher Tim Frayling of the Peninsula Medical School in Exeter, southwestern England. "Clearly, our results do not explain why one person will be six feet five inches (192 cms) and another only four feet 10 inches (145 cms). This is just the first of many that will be found, possibly as many as several hundred." Another step is to explain why HMGA2 has this effect. Researchers believe it plays a role in growth through regulating cell growth. Interest in "height" genes is spurred by more than idle curiosity, for there could also be a windfall in knowledge about disease. Taller people are statistically more likely to be at risk from some kinds of cancer (prostate, bladder and lung, for instance), which implies that genes that regulate cell multiplication may also play some part in letting cancer cells proliferate. Statistics also throw up an association between shortness and heart disease. "This is the first convincing result that explains how DNA can affect normal variation in human height," said US researcher Joel Hirschhorn of the Broad Institute, Massachusetts, and a professor of genetics at Harvard Medical School. "Because height is a complex trait, involving a variety of genetic and non-genetic factors, it can teach us valuable lessons about the genetic framework of other complex traits, such as diabetes, cancer and other common human diseases."