Book 1 Reading and Speaking (Л.Н. Шевырдяева - Naturally Speaking & Listening), страница 12

This effect was first observed in 1992. Recent studies, published in June in TheArchives of Internal Medicine, confirmed the finding.Still, some experts believe that coffee drinking, and particularly caffeine consumption, can have negativehealth consequences. A study published in January in The Journal of the American College of Cardiology, forexample, suggests that the amount of caffeine in two cups of coffee significantly decreases blood flow to the heart,particularly during exercise at high altitude.Rob van Dam, a Harvard scientist and the lead author of The Journal of the American Medical Associationreview, acknowledged that caffeine could increase blood pressure and slightly increase levels of the amino acidhomocysteine, possibly raising the risk for heart disease.

“I wouldn’t advise people to increase their consumption ofcoffee in order to lower their risk of disease,” Dr. van Dam said, “but the evidence is that for most people withoutspecific conditions, coffee is not detrimental to health. If people enjoy drinking it, it’s comforting to know that theydon’t have to be afraid of negative health effects.” (NY Times. August 15, 2006)Exercise 6. In the following text the lines are mixed up. Put them in their proper order. The first andthe last lines are in their correct places.Decaf Coffee Plants DevelopedBy Sarah GrahamFor many coffee lovers, their precious beverage comes with an unwanted ingredient: caffeine.

As a result,which solvents flush caffeine from the beans. Their next step is to apply their technique to C. arabica plants, whichproduce the high-quality Arabica coffee that accounts for 70 percent of the world market. Of course, it remains topercent less caffeine than regular plants do.Three enzymes are involved in making caffeine in coffee plants. Researchers at the Nara Institute of Sciencethe gene controlling one of these enzymes--theobromine synthase, or CaMXMT1--was repressed. Compared withprocesses have been developed to remove the compound, although current methods are expensive andregular plants, leaves from one-year-old GM plants exhibited a 50 to 70 percent reduction in caffeine content.from the plant.

Researchers report today in the journal Nature that their genetically modified coffee plants have 70apart from their low caffeine content at maturity."According to the report, "the transgenic plants described here should yield coffee beans that are essentially normalThe scientists note that their technique could sidestep some of the problems of industrial decaffeination, inand Technology in Japan led by Shinjiro Ogita engineered seedlings of Coffea canephora in which expression ofsometimes compromise flavor. But scientists may have come up with a way to get decaffeinated coffee straightbe seen if java lovers will embrace "GM joe." (From Scientific American Online, June 19, 2003)Exercise 7.

Make up a list of the 10 key facts about coffee. Agree on the final list of facts with thewhole group. Then summarize everything you now know about coffee into one report.30Unit 9. Human Genetics and DiversityI am the family face;Flesh perishes, I live on,Projecting trait and traceThrough time to times anon,And leaping from place to placeOver oblivion.Thomas HardyFrom a drop of water. .

. a logician could infer thepossibility of an Atlantic or a Niagara withouthaving seen or heard of one or the other. So all lifeis a great chain, the nature of which is knownwhenever we are shown a single link of it.Sir Arthur Conan Doyle A Study in ScarletExercise 1. What do you know about genetics? Explain the following terms in English:DNA, RNARibosomePhenotypeSelective breedingNucleic acidReplicationGenotypeHybridGeneTranscriptionEnhancerBreeding (crossing)GenomeTranslationPromoterInbreedingAlleleProcessingSilencerPure lineDominant / recessive geneSplicingTerminatorExercise 2. Discuss the following questions about genetic diversity of humans:1.

What role does genetic diversity of humans play?2. What genetic mechanisms control population diversity?3. To what degree are different ethnic groups genetically different?Exercise 3. Read the following two texts (Text A and Text B) about current genetic research of populationdiversity to check your answers in Exercise 2.Text A. How Our Genomes Control DiversityTwo research efforts have determined DNA recombination mechanisms that underlie population diversity, how ithappens and where in the genetic code it occursBy Nikhil SwaminathanTwo recent discoveries have shed new light on the source of diversity in the human population.

In one study,scientists examined patterns in DNA recombination, the process by which a person's genome is consolidated intoone set of chromosomes to pass onto an offspring. In the other, a link was made between variants of a particulargene and the extent to which DNA recombination occurs.In human testes and ovaries, where sperm cells and egg cells, respectively, are manufactured, sections ofchromosomes inherited from a person's parents are shuffled together to create a collage of genetic material that ispassed to offspring.

This process by which a new, unique set of chromosomes is created (with a mix of roughly halfthe material coming from each parent) is called DNA recombination and is the source of variation in populations."Recombination impacts population diversity," says George Coop, a postdoctoral fellow in human genetics at theUniversity of Chicago and co-author of an article that details variation in the pattern in which genes are shuffledfrom individual to individual.

"Recombination is the way that you generate novel haplotypes, novel combinations ofmutations." (Haplotypes are combinations of different versions of genes on a single chromosome that are inheritedas a unit.)Coop and colleagues in Science reveal the results of a high-resolution study designed to map the locationswhere recombination occurs—where one parent's genes have been swapped out for another. Using a population of725 Hutterites—communal farmers who settled in the Dakotas and Montana in the mid-19th century—the teamscanned genomes for 500,000 single-nucleotide polymorphisms (SNPs). SNPs mark points of genetic variation toestimate where DNA shuffles occurred. Researchers can tell which part of a child's genetic code came from whichof its four grandparents by comparing variants in both.The researchers noted nearly 25,000 total recombination events in analyses of 364 offspring.

Excluding thesex chromosomes, the team found that eggs typically showed 40 instances of recombination on each of theirchromosomes, whereas the chromosomes in sperm are typically made with 26 recombinational occurrences. TheUniversity of Chicago team also noted that as women age, more recombination takes place during meiosis (thecellular process that produces an egg).

In men, there is no age effect. Further, they noted that such incidentstended to focus on so-called "hot spots," locations where this crossover takes place often. Some turned out to begender specific, with females utilizing some recombination regions more often than males (and vice versa). The31usage of these zones of frequent recombination varied between individuals, but it seemed to be conserved amongfamilies, indicating that the extent and pattern of recombination may be inherited.Interestingly, a finding out of the Icelandic biotech firm deCODE genetics, also appearing in Science, shedslight on that last observation.

From a genome-wide analysis looking at 300,000 SNPs in 20,000 people, deCODEscientists were able to find two locations on a gene found on chromosome 4 and link variations at those two localesto the recombination rate. "What's interesting about the SNPs is that the variants have opposite effects on thesexes," says deCODE's chief executive officer Kari Stefansson. According to the new study, one of the locations onthe gene, known as RNF212, is associated with high rates of recombination in men, but low rates in women; for theother marker, the gender effect is reversed.

"If you were going to design a mechanism to keep rates within [certain]limits you would do exactly this," Stefansson explains about the gender paradigm. "For one generation, it leads tohigher recombination rate; for the next generation, it would lead to a lower recombination rate." Overall, the twopositions can account for 22 percent of the variability in a man's recombination rate and 6.5 percent of thevariability in a female's, the study says.Chicago's Coop lauded the deCODE efforts, noting that this was the first mapping of a gene that influencesrecombination in mammals.

"I would imagine that the variation that we see in individuals is in part caused by theseSNPs," he says. "I think this represents a big step forward in determining the events of human recombination."(From Scientific American Online, February 5, 2008)Text B. Ethnic Differences Traced to Variable Gene ExpressionFinding could explain why ethnic groups suffer from particular common diseasesBy Nikhil SwaminathanTay-Sachs disease seems to favor Jews of Eastern European descent. Cystic fibrosis has an affinity forCaucasians.