Text 3.1. DNA Structure

■ Essential targets:

By the end of this text you should be able to:

● distinguish between a nucleoside, a nucleotide, and a polynucleotide;

● explain how a phosphodiester bond forms;

● discuss the significance of complementary base pairing in DNA.

Pre-reading

Working in pairs, try and answer the following questions before you read the text. Don`t be afraid of guessing the answers! When you have finished, check your answers by reading the text.

1. Who discovered the structure of DNA?

2. What do you know about a nucleoside and a nucleotide?

3. What shape does a molecule of DNA have?

4. What kind of information does a molecule of DNA contain?

Exercise A. Match the words with their definitions:

	to join	A	only one or considered to its own
	base	B	serious study of a subject that is intended to discover new facts or test new ideas
	ring	C	to connect or fasten things together
	support	D	the most important part of something from which new ideas develop
	bond	E	a circular line or mark
	single	F	sympathetic encouragement and help that you give to someone
	research	G	the chemical force that holds atoms together
	to discover	H	a single thin piece of thread, wire, hair etc.
	double	I	something that is twice the size, quantity, value, or strength of something else
	strand	J	to find something that was hidden or that people did not know about before

■ Read the given text and make your essential assignments:

The description of the double helical structure of DNA (deoxyribonucleic acid) by Watson and Crick in 1953 (see Fact of life) was a landmark in science history. Their discovery sparked off a new era in scientific research which has had, and will continue to have, far-reaching consequences.