| either ... or | àáî ... àáî | You may choose to study either English or French. Âè ìîæåòå âèáðàòè, ùî âèâ÷àòè – àáî àíãë³éñüêó, àáî ôðàíöóçüêó. |
| neither ... nor | í³ ... í³ | Neither wind nor low temperature could stop the travellers. Àí³ â³òåð, àí³ íèçüêà òåìïåðàòóðà íå ìîãëè çóïèíèòè ìàíäð³âíèê³â. |
². Decide which of these statements are true and which are false.
1. The Internet is a global system of computer networks connected by a wide range of electronic and optical networking technologies. 2. TV programs have been transformed into Web sites, blogging, and web feeds. 3. The Internet was created as forceful computer networks in the 1960s in the USA for military purposes. 4. The terms Internet and World Wide Web are one and the same.
²². Answer the following questions.
1. What is the Internet? 2. What traditional communication media give rise to services such as Voice over Internet Protocol (VoIP) and IPTV? 3. What new forms of human communications were created in the Internet? 4. When was the Internet created?
Text 13. DNA Stretching Mystery is Solved
Active Vocabulary:
| to unravel | ðîçïëóòóâàòè | bead | êóëüêà, áóëüáàøêà |
| mystery | òàºìíèöÿ | to pull apart | ðîçðèâàòè |
| to stretch | íàòÿãóâàòèñÿ | tweezing | ðîçùåïëåííÿ |
| breaking point | ìåæà ì³öíîñò³ | zipper | çì³éêà |
| researcher | äîñë³äíèê | transition | ïåðåì³ùóâàííÿ |
| to carry out | âèêîíóâàòè | tension | íàïðóãà |
| to attach | ïðèºäíóâàòè | strand | ëàíöþæîê ìîëåêóë |
Researchers in Europe have unravelled a mystery that has been puzzling scientists for years: what happens to a molecule of DNA when it is stretched to its breaking point.
Now Erwin Peterman and his colleagues appear to have answered the question. The researchers carried out a DNA-stretching experiment by attaching one end of each strand of a length of double-stranded DNA to a polystyrene bead. The beads could be pulled apart with a controlled and measurable force by lasers – a process called optical tweezing.
“Pulling the DNA from both ends is a bit like pulling on a jacket that has a double-ended zipper,” says Peterman. “What we found was that at the transition force the zipper starts to come apart at either end, but remains zipped in the middle. In other words, the DNA comes apart at either end, and under tension this single-stranded DNA is 70 percent longer than double-stranded DNA.”
It is a great work. It tells us about the way the structure of a single molecule is changing under tension, something we have not been able to see before. It looks as though they have solved the question, but as always it is very complicated. So this might not be the end of the story.