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 2017-12-21 |
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By JR Minkel
Researchers have designed a new type of DNA computer that works in human cells, perhaps paving the way for a distant technology capable of picking out diseased cells from otherwise healthy tissue. The system runs on a process called RNA interference (RNAi) in which small molecules of RNA prevent a gene from producing protein.
The goal is to inject human cells with DNA that can determine whether a cell is cancerous or otherwise diseased, based solely on the mix of molecules inside the cell. Sensing disease, the DNA might trigger a pinpoint dose of treatment in response. That technology, however, is a long way off. For now, researchers are testing different ways of turning DNA into versatile computers that can detect certain combinations of molecules and respond by producing other molecules.
«The central challenge is how do you create a 'molecular computer' capable of making decisions», says bioengineer Yaakov Benenson of Harvard University. Researchers have designed powerful test tube DNA computers that could play tic-tac-toe or perform the basic tasks of logic, but getting them to work in human cells was likely to be tricky, Benenson says.
RNAi is something that cells do naturally. Cells produce what are known as short interfering RNA (siRNA) molecules, which recognize corresponding DNA sequences in genes and cause them to shut down.
Benenson and colleagues engineered a target gene to be sensitive to several different siRNAs of their own design. In the simplest case, they introduced a single siRNA molecule to switch off a target gene that encoded a fluorescent protein. In more complex cases, a pair of siRNAs or either of two siRNAs switched off another target gene, which in turn switched off a gene for a fluorescent protein. To make sure the system worked as intended, the researchers based their siRNAs on those of other species, they report in a paper published online today by Nature Biotechnology.
In principle, the RNAi technique can reach great heights of complexity, Benenson says, by making genes sensitive to more and more siRNAs in various combinations. «The scalability is very important, because eventually you want to make complex decisions», he says.
He says the next step is figuring out how to make the molecules inside a cell – such as those that are overproduced in cancer – trigger the production of siRNAs.
(«Scientific American», May, 2007)
Вопросы:
1. What is the main goal of DNA computers?
2. What does RNAi stand for?
3. What are the prospects of the RNAi technique?
2.2. Прочитайте статью, ответьте на вопросы, затем составьте реферат статьи на русском языке:
New Zealand scientists record 'biodiversity breakdown'
By Neil Bowdler
Scientists in New Zealand say they have linked the modern-day decline of a common forest shrub with the local extinction of two pollinating birds over a century ago. They say the disappearance of two birds – the bellbird and stitch bird – from the upper North Island of the country has lead to a slow decline in common plants, including the forest shrub New Zealand gloxinia.
Ship rats and stoats imported into the country around the year 1870 are blamed for the birds' demise.
The researchers claim the study, published in the journal Science, offers rare experimental proof of a breakdown in a local ecosystem.
New Zealand gloxinia or Rhabdothamnus solandri is a gangly forest shrub, which grows in the shade to about 2m high and produces an orange tubular flower. It depends on three birds for pollination – the bellbird, stitch bird and the tui.
While the latter now seems only to feed higher up in the forest canopy, the former two vanished from upper North Island in the late 19th century. It is thought they were killed off by rats brought in by ships or by stoats introduced to control the local rabbit population.
The researchers wanted to observe the impact on New Zealand gloxinia of these disappearing bird populations and so compared the situation on the mainland with that of three nearby island bird sanctuaries where the birds remain abundant.
What they found was that pollination rates were vastly reduced on the mainland with seed production per flower 84 % lower compared with the islands.
While this has yet to fully manifest itself in the density of adult gloxinia populations on the mainland, the researchers found 55 % fewer juvenile plants per adult plant on the mainland vis-à-vis the islands.
A shoot of New Zealand gloxinia, showing the bird-pollinated flower and its hairy leaves.
The researchers could also quantify how often – or how little – birds visited the plant, as birds make distinct markings on the flower as they feed on the nectar.
«This plant is in trouble but it's a slow motion disaster», said Professor Dave Kelly of New Zealand's University of Canterbury, who led the research. «It hasn't been well pollinated for about the last 140 years – that's about when these birds disappeared off the North Island».
«In that time there haven't been enough seedlings coming through and so the plant is quietly crumbling away, fading away».
(«Science report», BBC News)
Вопросы:
1. What has lead to a slow decline in common plants, including the forest shrub New Zealand gloxinia?
2. What do scientists in New Zealand link the modern-day of a common forest shrub with?
3. How do the researchers quantity how often – or how little – birds visited the plant?
2.3. Перепишите предложение, заполнив пропуски подходящим по смыслу словом:
1. A Nobel never … any reward for what he had done.
a) expected; b) refused; c) noticed; d) avoided.
2. In Sweden A. Nobel began his own study of ….
a) weapon; b) explosives; c) substances; d) literature.
3. They found … old books in the library.
a) so; b) peace; c) plenty of; d) never.
4. I usually get up early in the morning go to the bathroom and … have breakfast.
a) then; b) too; c) yet; d) however.
5. It was an ordinary day but … an explosion occurred in the old mine.
a) few; b) really; c) nobody; d) suddenly.
6. He looked … and saw the dog running after him.
a) back; b) for; c) seldom; d) really.
7. He refused to give his … explanation.
a) meaning; b) own; c) opportunity; d) justice.
8. The explosion … in the old mine.
a) make; b) were; c) occurred; d) brought.
9. The students worked hard during the term and achieved … results.
a) excellent; b) bad; c) terrible; d) few.
10. When I have holidays I have … free time and can do anything.
a) little; b) a few; c) plenty of; d) huge.
11. His invention was used for war to kill and … people.
a) justify; b) avoid; c) injure; d) care for.
12. He realized that without the experiment his work would be....
a) useful; b) successful; c) necessary; d) useless.
13. It is important to take measures to … the risk of fire.
a) avoid; b) choose; c) need; d) win.
14. I … a good mark for the answer.
a) mastered; b) invented; c) deserved; d) passed.
15. When she was abroad she … her furniture in a warehouse.
a) left; b) sold; c) stored; d) gave.
16. That’s not the … way to stop the machine.
a) proper; b) necessary; c) reasonable; d) essential.
17. I couldn’t find a parking ….
a) territory; b) space; c) field; d) site.
18. The bag was covered with a sticky ….
a) substance; b) matter; c) component; d) mixture.
19. Have you anything … to this material but cheaper?
a) familiar; b) known; c) similar; d) same.
20. … nations sometimes try to control weaker countries.
a) Powerful; b) Advanced; c) Effective; Efficient.
21. The wire had … in half.
a) unite; b) divide; c) split; d) separate.
22. She gave us a short … of the rules before we started.
a) definition; b) explanation; c) annotation; d) description.
23. Many plants have medicinal ….
a) characteristics; b) qualities; c) features; d) properties.
24. The main … of the country’s industry is ship building.
a) branch; b) department; c) space; d) seat.
25. Scientists believe that ghosts do not ….
b) look; b) exist; c) believe; d) stay.
26. The company … twice last year.
a) doubled; b) established; c) founded; d) expanded.
27. The experiment gave us … data on this problem.
a) considerable; b) long; c)strong; d) huge;
28. The main … of the plane crash was bad weather.
a) question; b) substance; c) reason; d) problem.
29. The … of this system was held last year.
a) quality; b) improvement; c) quantity; d) problem.
30. The article was about how the scientists … the distance to the moon.
a) counted; b) enumerated; c) calculated; d) computed.
31. There are many cities with a … of over 2 million people.
a) people; b) inhabitants; c) population; d) residents.
32. Great spending on education is expected to lead to a large … in the number of students.
a) growth; b) rise; c) increase; d) escalation;
33. Our university has excellent sporting ….
a) facilities; b) equipment; c) conditions; d) resources.
34. I regret that a … meeting prevents me from accepting your invitation.
a) antecedent; b) future; c) early; d) previous.
35. It would … matters if you were more cooperative.
a) ease; b) help; c) facilitate; d) lighten.
36. Having read the message I came to a … decision.
a) brisk; b) hurried; c) prompt; d) rapid.
37. The house has many interesting … including a large Victorian fireplace.
a) feature; b) characteristic; c) property; d) peculiarity.
38. Is the story a complete invention, or is it … on fact?
a) written; b) told; c) founded; d) established.
39. A paint that gives woodwork … protection against the weather.
a) permanent; b) lasting; c) unending; d) stable.
40. A … of well-qualified people have recently left the company.
а) amount; b) digit; c) numeral; d) number.
2.4. Вопросы для самопроверки:
1. Каковы основные способы достижения лаконичности при составлении реферата?
2. Можно ли давать субъективную оценку содержанию первичного текста при составлении реферата?
3. Можно ли пересказывать содержание документа (выводы, рекомендации, фактический материал) при составлении аннотации?
4. Какие аспекты содержания исходного документа вы включили в реферат?
5. Какие аспекты содержания включаются в аннотацию?
6. Чем отличается аннотация от реферата?
Вариант 3
3.1. Прочитайте статью, ответьте на вопросы, затем составьте аннотацию к статье на английском языке:
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