VII. Answer the following questions. Use all information given before.

1. Who and when published the first description of the DNA structure?

2. What information did Watson and Crick use for their model?

3. Why did not Rosalind Franklin receive a Nobel Prize?

4. What is each DNA strand made of?

5. What is a condensation reaction?

6. What does each nucleotide consist of?

7. What is the main difference between purines and pyrimidines?

8. What is the main condition for complementary base pairing to happen?

9. Distinguish between a nucleoside and a nucleotide.

10. What type of chemical reaction forms a phosphodiester bond?

11. If one strand of DNA has the base sequence AATCCG, what will be the corresponding base sequence of bits complementary strand?

VIII. Read and translate the short text without any dictionary:

Fact of life:

In April 1953, the biologist James Watson and the physicist Francis Crick published the first description of the structure of DNA, in a letter to the journal Nature. They based their description on a model they had constructed, but they did little experimental work themselves. The information they used for their model came from work carried out by Erwin Chargaff on the base composition of DNA , and X-ray data obtained by Rosalind Franklin, working with Maurice Wilkins at King's College, London. One particularly good X-ray diffraction photograph obtained by Franklin in the winter of 1952-3 gave crucial support to the idea that DNA has a helical structure. Other data from Franklin showed that DNA has two strands, not three or more as some scientists had proposed. In 1962, Watson, Crick, and Wilkins received a Nobel Prize for their discoveries. Tragically, Rosalind Franklin died of cancer in 1958 at the age of 37. Nobel prizes cannot be given posthumously.

IX. Food for thought:

In 1948 the chemist Ervin Chargaff began using paper chromatography to analyses the base composition of DNA from a number of species. Table 1 shows the types of results may be interpreted to support Watson and Crick’s double-helix hypothesis. What other interpretations could be given?

X.Translate into English using all the active possible:

1. Описание структуры ДНК в виде двойной спирали было поворотным пунктом в истории науки.

2. Это открытие явило новую эру в научном исследовании, которое Кимеет и будет иметь далеко идущие последствия.

3. Реакция конденсации (уплотнения) приводит к отщеплению молекулы воды.

4. Нуклеотиды объединяются и образуют длинные неразветвленные полинуклеотидные цепи.

5. ДНК состоит из двух полинуклеотидных цепей скрученных вокруг друг друга и образующих двойную спираль.

6. Модель ДНК Уотсона и Крика показала, что базовые пары располагаются в 0.34 нм друг от друга.

7. Таким образом, последовательность баз вдоль одной полинуклеотидной цепи определяет последовательность вдоль другой: аденин в одной цепи означает, что в той же точке другой цепи должен быть тимин и так далее.

8. Органические основания, присутствующие в ДНК, являются либо пуринами, либо пиримидирами.