Forget Everything You Learned in School About Chromosones

Science taught us lots of things in school…. Matter, DNA, the Solar System—well, you get it. But those of us who paid attention and stayed awake when our teachers discussed chromosones now discover—were our instructors ever wrong! Here’s the scoop from the New York Times...

January 14, 2010

Male Chromosome May Evolve Fastest

By NICHOLAS WADE

A new look at the human Y chromosome has overturned longstanding ideas about its evolutionary history. Far from being in a state of decay, the Y chromosome is the fastest-changing part of the human genome and is constantly renewing itself. This is “a result as unexpected as it is stunning — truly amazing,” said Scott Hawley, a chromosome expert at the Stowers Institute in Kansas City, Mo. The Y chromosome makes its owner male because it carries the male-determining gene. Boys are born with one Y and one X chromosome in all their body’s cells, while girls have two X’s. The other 22 pairs of chromosomes in which the human genome is packaged are the same in both sexes. The Y chromosome’s rapid rate of evolutionary change does not mean that men are evolving faster than women. But its furious innovation is likely to be having reverberations elsewhere in the human genome. The finding was reported online on Wednesday in the journal Nature by a team led by Jennifer Hughes and David Page of the Whitehead Institute in Cambridge, Mass. In 2003, Dr. Page, working with scientists at the Washington University School of Medicine, decoded the DNA sequence of the human Y chromosome. He and the same Washington University genome team have now decoded the chimpanzee Y chromosome, providing for the first time a reference against which to assess the evolutionary history of the human Y. The chimpanzee and human lineages shared a common ancestor just six million years ago, a short slice of evolutionary time. Over all, the genomes of the two species are very similar and differ in less than 1 percent of their DNA. But the Y chromosomes differ in 30 percent of their DNA, meaning that these chromosomes are changing far faster in both species than the rest of the genome. In the case of chimps, their mating habits are probably the source of the fierce evolutionary pressure on their Y chromosome. When a female comes into heat, she mates with all the males in the group, setting up competition within her reproductive tract between the sperm of different males. Many genes that govern sperm production are situated on the Y chromosome, and any genetic variation that improves a chimp’s chances of fatherhood will be favored and quickly spread through the population. Sperm competition may have been important in the earliest humans, too, for some years after the chimp and human lineages split. Sperm competition could still play a role in human reproduction, some experts think, given the trickle of cases of heteropaternity, the birth of twins with different fathers. Another reason for the intensity of selective pressures on the Y chromosome in both chimps and humans may be that natural selection sees it as a single unit, so a change in any one of its genes affects the survival of all the rest. On the other chromosomes, selection is more focused on individual genes because chunks of DNA are swapped between the members of each pair of chromosomes before the generation of eggs and sperm. This DNA swapping process is forbidden between the X and the Y pair, keeping the male-determining gene from being transferred into the X chromosome, creating gender chaos. But this prohibition has caused most of the genes on the Y chromosome to decay for lack of fitness. In the rest of the genome, a gene damaged by a mutation can be swapped out for the good copy on the other chromosome. In the Y, which originally had the same set of genes as the X, most of the X-related genes have disappeared over the last 200 million years. Until now, many biologists have assumed either that the Y chromosome was headed for eventual extinction, or that its evolutionary downslide was largely over and it has sunk into stagnation. Dr. Page’s new finding is surprising because it shows that the Y chromosome has achieved an unexpected salvation. The hallmark of the Y chromosome now turns out to be renewal and reinvigoration, once the unnecessary burden of X-related genes has been shed. “Natural selection is shaping the Y and keeping it vital to a degree that is really at odds with the idea of the last 50 years of a rotting Y chromosome,” Dr. Page said. “It is now clear that the Y chromosome is by far the most rapidly evolving part of the human and chimp genomes.” This does not mean that men are evolving faster than women, given that the two belong to the same species, but it could be that the Y’s rate of change drives or influences the evolution of the rest of the human genome in ways that now need to be assessed. It would be “hard to imagine that these dramatic changes in the Y don’t have broader consequences,” Dr. Page said. Andrew Clark, a geneticist who works on the Y chromosome at Cornell University, said the Y’s fast turnover of DNA could effect the activity of genes throughout the genome, because just such an effect has been detected in laboratory fruit flies. The decoding of the Y chromosome’s DNA was particularly difficult because the chromosome is full of palindromes — runs of DNA that read the same backward as forward — and repetitive sequences that confuse the decoding systems. Decoding the human Y took 13 years, and the chimp Y took eight years, Dr. Page said.

What Do They Know That We Don’t?

While we’re scrambling here in the United States to keep from getting sick by washing our hands and getting shots, the Chinese have a totally different approach  to stay healthy—and it’s becoming something of a benefit to Americans… The story from Yahoo…

Garlic prices soar in China amid flu fears

Yahoo! Buzz
By Calum MacLeod, USA TODAY
BEIJING — Wrapped up in earmuffs and a heavy jacket to fight the Beijing winter, Liu Zhan shows little sign of soaring wealth. Until he removes his gloves — and reveals a large gold ring. At the Chinese capital’s biggest vegetable wholesale market, other traders call him “Millionaire Liu.”

The pungent root of that nickname is stacked in bags on and around Liu’s haulage truck. Garlic prices have jumped so high in China that the crop has outperformed gold and stocks to be the country’s best performing asset this year.

As H1N1 swine flu continues to worry China’s leaders — who are rolling out a nationwide vaccine program — its people seek a more traditional remedy. Just as some Chinese turned to turnips to prevent the SARS virus in 2003, garlic has emerged as a swine flu fighter in 2009.

“Garlic kills bacteria, and I eat at least half a bulb each day,” says Liu, 43, whose prices have leapt from just five cents a pound in February to almost 55 cents today.

Although Chinese government experts have cautioned consumers about the lack of scientific proof for garlic’s flu-killing powers, its supporters remain adamant. “Garlic can definitely help prevent swine flu,” claims Li Jingfeng, chairman of the Jinxiang Garlic Association in eastern China’s Shandong province.

Self-promoted as China’s “hometown of garlic,” Jinxiang county grows a quarter of all garlic in China, which in turn provides more than a quarter of global output, says Wang Hao, marketing manager for the China Garlic website. Jinxiang, whose name means Gold Village, has enjoyed its best-ever sales year, says Li.

“Next year, the price will be even higher, but our American and European buyers still think it’s cheap, as garlic sells for $6.60 for a pound in their countries,” he says.

A windfall for U.S. producers

The Chinese price hike has been a boon to U.S. garlic producers, says Bill Christopher, owner of Christopher Ranch in Gilroy, Calif., the largest U.S. garlic producer.

“There’s a lot less Chinese garlic being shipped over here, and what is being shipped is being shipped at prices three times more than last year,” Christopher says. “There’s a bit of a world shortage and of course that raises the price.”

Chinese garlic usually accounts for 90% of the U.S. import market, which supplies more than half of the bulbs consumed in the nation, Christopher says. This year, the Chinese have shipped about half the usual 200 million pounds of garlic, and the price has tripled since last year, from about $8 to $24 for a 30-pound box. For U.S. producers, whose higher quality bulbs sell for $40 to $50 a box and are marketed to restaurant chefs, prices have risen 15% to 20%, he says.

The cost of U.S. garlic rises every year, in part because of ongoing water shortages in California, “but (this year) that’s more than going to be offset by increases in the sale price due to the Chinese not shipping as much garlic,” Christopher says.

H1N1 only partly explains the garlic fever, Li says. Rising prices in 2006 sparked a rush to plant garlic that created a market glut over the next two years. Falling acreage and bad weather combined to leave suppliers in the driver’s seat this year, he says.

The real winners appear to be speculators such as Shao Mingqing, a jobless 22-year-old who borrowed money to buy 100 tons of garlic in September, then made a $59,000 profit selling in October, the state-run China Daily reports. He now drives a $26,360 Toyota, it says.

The volatile nature of the garlic market is typical of a cyclical product, says Chen Shuwei, an analyst at Beijing Orient Agribusiness Consultants. “There is a lot of money in China, but private businessmen don’t have many avenues for investment as state-owned companies control many large industries. But it’s easy for them to enter a sector like garlic and make some short-term profits.

“Their money may head to another product soon,” he warns.

While Beijing closely watches potential bubbles in key industries such as real estate, the pricey bulb remains a minor concern, Chen says.

“The price of garlic is rising, and Chinese people need it for their daily cooking, but the rise does not have a big impact on household consumption, and matters less than key crops like corn and wheat,” he says.

Sticker shock

The soaring costs still raise eyebrows on China’s streets. “How can it be this expensive?” asks Zhao Wenjing, a Beijing nurse buying garlic Monday. “I haven’t cooked for a long time, but I heard some doctors said it could prevent H1N1, so I came to buy some, although I don’t actually like the smell,” says Zhao, 26.

Unlike some Chinese business booms, the garlic surge might help American businesses, at least in the short term. Garlic growers in the USA have long complained about their Chinese competition.

“Chinese garlic’s major price bump is a boon for California growers looking to recoup business that has been lost to cheaper Chinese garlic,” reads a blog post on the site of a major California grower.

Contributing: Oren Dorell in McLean, Va.