Биология в современном мире. Учебное пособие

2)It is by means of such binding that a protein performs its function.

3)It was after he had returned from Moscow that I told him the truth.

4)Ch. Darwin was the first who began to speak about origin of species and natural selection.

7.9 Exercise 9

Read the text. Translate it.

The chromosome structure.

When chromosomes, the carriers of genetic information in higher cells, were first observed through a microscope some 100 years ago, they were seen as dense, ropelike bodies moving in two groups toward opposite poles of a dividing cell. The chromosomes could be followed as each group was incorporated in one of two daughter cells and then enclosed in a membrane – bounded nucleus. Then, a strange thing happened: the chromosomes seemed to disappear. They had not, of course, really vanished. They had simply become so thin and diffuse as to be invisible in the microscope. Having been highly condensed during cell division to facilitate their movement, the chromosomes had opened up to expose the genetic information needed for the daughter cells’ growth and function.

The information in chromosomes is divided into the units called genes, many thousands of which are arrayed along the length of the chromosomal material in a typical plant or animal cell. Genes specify the structure of proteins which in turn carry out cellular functions. These functions differ for different cell types: blood cells, liver cells, brain cells and so on. The sets of proteins each cell type manufactures are therefore different. Yet every cell of an organism contains the same genes. What differs from cell to cell and from time to time is which genes are expressed, or translated into proteins.

The necessary selectivity in the expression of genetic information is accompanied by, and may be the consequence of, selectivity in the unfolding of chromosomes: only the gene regions that are being expressed in a particular cell at a

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particular time are maximally unfolded and exposed. The great variety of cell types is therefore reflected in an extraordinary diversity of chromosome form and structure. What is the basis of that diversity? The structural flexibility of chromosomes has to account not only for selective expression but also for the inclusion, within a cell nucleus less that a hundredth of a millimeter in diameter, of chromosomal material that has a total length (in its most expanded form) of about two meters.

The first studies of chromosomes focused on a mystery of their composition. The chromosomes of higher cells are composed of the substance called chromatin, which consists of two kinds of chemical compound: protein and the nucleic acid DNA. Although protein is the more abundant component, all the genetic information of chromatin resides in the DNA. Why then is there so much protein? This question is made particularly intriguing by the nature of the protein. By the early 1970’s of the 20th century it was apparent from the work of many investigators that the protein component of chromatin consists largely of just five types known as histones. The same five histones are found throughout the wide range of organisms whose chromatin is contained in a nucleus, from comparatively simple ones such as yeasts and moulds to the most complex, including man. A major goal has been to dispel the mystery of the histones by finding out where in a chromosome they are and what they do.

The first indication of the role of histones came almost 50 years ago from X – ray – diffraction studies of chromatin carried out by English and French investigators. X – ray diffraction is a technique for the study of repeating structures (for example crystals) in which a pattern of atoms or molecules is repeated over and over again in a three – dimensional array.

The scientists got a striking result: they found evidence for a repeating structure in chromatin. The degree of order was rather low compared with that of crystals, but nonetheless a repeat was clearly visible. Moreover, the same repeat could be demonstrated in a mixture of histones and DNA. Analysis of the X – ray data indicated that the repeat comes at intervals of about 100 angstroms.

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7.10 Exercise 10

1)Answer the following questions.

2)What are chromosomes? (…the carriers of genetic information).

3)What did they look like when they were first observed through a

microscope? (…dense, ropelike bodies).

4) Why did the chromosomes seem gradually to disappear? (…to expose the genetic information needed for the daughter cells’ growth and function).

5)Where are many thousands of genes arrayed? (…along the chromosomal material…).

6)What substances carry out cellular functions (…proteins).

7)There exists a great variety of cell types, doesn’t there? What is this great variety reflected in? (…in a diversity of chromosome form and structure…).

8)How long is a cell nucleus? How long is the chromosomal material?

9)What kind of substance are the chromosomes of higher cells composed?

(…chromatin).

10)What does the chromatin consist of? (…protein and DNA).

11)What is the DNA? (…nucleic acid).

12)What does the protein component of the chromatin consist of? (…histones).

13)How many types of histones exist?

14)It what way did English and French investigators use the technique of X – ray diffraction while studying the chromatin?(…as in the case with crystals).

15)What did the analysis of X – ray data indicate? (…of intervals of about 100

angstroms).

7.11 Exercise 11

Fill in the sentences with suitable terms from the text.

1)Chromosomes are ……… of genetic information.

2)Through the microscope they are seen as ……… .

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3)The information in chromosomes is divided into the units called ……… .

4)Genes carry out cellular ……… .

5)These functions differ for ……… .

6)Each cell type manufactures different sets of ……… .

7)Every cell of the organism contains the same ……… .

8)Genes are expressed and translated into proteins by ……… .

9)The great variety of cell types is reflected in ……… .

10)A cell nucleus is less ………, while the chromosomal material has ……….

7.12 Exercise 12

Write down from the text all the biological terms, and mind them.

7.13 Exercise 13

Study the scheme and retell about the chromosome structure, using the following verb groups: to be composed; to include, to reside, to have; one can find; to repeat; to occur = to take place; to be known, figure 6.

Figure 6 - Exercise 13

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7.14 Exercise 14

Translate the sentences into English using the words and the scheme above.

1)Хромосомы состоят из вещества известного как хроматин.

2)Хроматин включает в себя два вида химических соединений: протеин

инуклеиновую кислоту ДНК.

3)Протеина в хроматине больше, чем ДНК.

4)Но вся информация находится в ДНК.

5)Протеиновый компонент хроматина содержит 5 типов гистонов.

6)Эти гистоны можно найти в любых организмах: в таких простых, как дрожжи и плесень, и в самых сложных, в том числе у человека.

7)У гистонов повторяющаяся структура как и у кристаллов, в которых модель (a pattern) атомов или молекул повторяется снова и снова в трехмерной цепочке.

8)Такую повторяющуюся структуру можно обнаружить в соединении

(mixture) гистонов и ДНК.

9) Повторение происходит с интервалом в 100 ангстрoмов.

7.15 Exercise 15

Summarise the information about the chromosome structure and retell about it.

7.16 Exercise 16

Translate two last paragraphs of the text in written form.

7.17 Exercise 17

Read the text. Discuss it with your partner: ask questions, share your opinions, make up your schemes.

The structure of proteins and DNA.

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To understand the order within chromatin it is necessary to consider the structure of proteins and of DNA. A protein is a chain of the 20 kinds of building blocks called amino acids. The chain spontaneously folds on itself in a manner dictated very precisely by the sequence of amino acids. The folded structure is usually compact except for cavities (впадина) or protrusions (выступ) on its surface that serve as sites for binding selectively to other molecules. It is by means of such binding that a protein performs its function. For example, enzymes bind to other molecules and catalize their chemical transformation; antibodies play a key role in the immune response by binding to any foreign substance that enters the body. Histones perform their function in chromatin by binding to DNA by means of an ionic interaction: many of the amino acids in histones are positively charged and associate with negatively charged groups in the DNA.

The consequences for the configuration of DNA are profound. DNA is long and thin; a single DNA molecule runs the length of a chromosome. The DNA molecule consists of two chains of the building blocks called nucleotides and the sequence of the nucleotides constitutes the genetic message. The chains are wound around each other, and the resulting cablelike double helix is fairly stiff. This slender rod has no features that recur (повторяться) at intervals of 100 angstroms. Yet when the DNA is combined with histones in a chromatin, a 100 – angstrom repeat of structure is observed. One possible interpretation would be that histones bind to the DNA in such a way as to constrain (сжимать) it into a pattern of folding or coiling (свертываться в спираль) that has a period of 100 angstroms, performing an architectural function required for the organization of DNA in chromatin.

7.18 Exercise 18

Describe the DNA and protein structure. Study the information under the schemes, figure 7

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Figure 7 - Exercise 18

8 Lesson 8. The 21st century biology (Биология в 21 веке)

8.1 Exercise 1

Mind the following words and set expressions.

1)to center on smth – сосредоточиться на ч-л.

2)to pave the road – проложить дорогу.

3)comprehensive studies – всесторонние изучения.

4)tangible – осязаемый, реальный.

5)low molecular compound – низко – молекулярное соединение.

6)to endorse the draft – подтвердить проект.

7)scrutinity = research = investigation – исследование.

8)aforesaid – вышеупомянутый.

9)the scroll of human life – спираль человеческой жизни.

10)to be doomed to extinction – быть обреченным на вымирание.

11)to enjoy the recognition – пользоваться признанием.

12)to come to conclusion – придти к заключению.

13)from the point of view – с точки зрения.

14)a great deal = much = a lot of – много.

15)as such – как таковой, по существу.

16)to remain obscure – оставаться неясным.

17)to know for sure – знать наверняка.

18)to be aware of =to know– знать.

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8.2 Exercise 2

Mind the following verbs.

to evolve – развертывать; to undertake (undertook - undertaken)

предпринимать; to distinguish = to differ = to vary – отличаться; to confine –

ограничивать; to pinpoint – точно определить; to afflict – огорчать; to inhibit –

подавлять; to warn – предупреждать, to distort – искажать, to deny – отрицать; to assume = to suppose – предполагать; to replicate = to recur = to repeat – повторять; to ensure – обеспечивать; to eliminate – уничтожать; to prolifirate –

размножаться; to deal (dealt) иметь дело.

8.3 Exercise 3

Read and translate the following groups of words. Use a dictionary if necessary.

1)to order – order – orderliness – orderly; in order to; hereditary disorders.

2)to dispense – dispensable – dispensation; dispensary – dispensatory; indispensable part of studies.

3)to distort – distortion – distortionist – genetic distortions.

4)to repeat – repeated – on repeated occasions; repeatedly, repeater, repeating; repeatable – unrepeatable; history repeats itself; repetition; repeating properties of DNA.

5)to inherit – heredity – hereditary; inheritance, disinherit, human heredity; cultural heritage; heritable, heritor.

8.4 Exercise 4

Read and translate the following word – phrases. Pay attention to the attributes. genetic research; the intricate genetic mechanisms determining human heredity; the human genome program; a truly international effort undertaken by

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scientists; comprehensive studies; the substance directly responsible for heredity; tangibale chemical structure; simple low – molecular compounds; extended thread – like structures; human body cells; a considerable social problem; one single cell being damaged; a damaged cell; harmful mutations; a stern warning to the human race; analytical information – computer programs; discoveries made in the latter half of the century; the most complicated and contradictory process; so – called recurrences.

c) мы должны знать наверняка; d) мы можем знать наверняка.

8.6 Exercise 6

Translate the sentences. Pay attention to the underlined grammar and lexical phenomena.

1) But as late as the middle of the 20th century genome remained but an abstract “unit” of heredity.

2)The DNA fits into a cell of not more than 20 microns in diameter.

3)It is these “words” and “phrases” that contain the commands.

4)What is more, most types of cancer are afflictions of the genome, which start with its one single cell, being damaged.

5)Because of genetic distortions homo sapiens is doomed to extinction as a species sooner or later.

6)Pathological genes can either destroy or make us ill.

7)It was then that scientists came to the conclusion.

8)But it is proteins alone that can put this information into practical use.

9)DNA replicates many times over.

10)DNA molecules are the only ones in our body which contain everything necessary for self reproduction.

8.7 Exercise 7

Read and translate the sentences. Pay attention to the meaning of the verbs

“should” and “would”.

1)The American geneticist warned that the homo sapiens as a species would extinct because of genetic distortions.

2)We should live longer if our cells did not destroy.

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