Биология в современном мире. Учебное пособие

3) It is necessary that the Human Genome Program should play an essential

role in the mankind’s life.

4)The scientists should study DNA more thoroughly.

5)The genome would have been told about at the beginning of the 20th

century if it had been discovered.

6) The scientists warn us about the danger of polluting the environment but

we wouldn’t listen to them.

8.8 Exercise 8

1)Put 4 types of questions to the following sentences.

2)The problem became the focal point of scrutinity by scientists.

3)The human genome consists of 23 pairs of chromosomes.

4)One has to say a few words about the “language” carrying genetic

information.

8.9 Exercise 9

Read the text, translate it.

A glimpse into the 21st century biology.

Genetic research in general and studies into the intricate genetic mechanisms determining human heredity take a prominent, if not the leading place within the context of the modern biological and also medical sciences. Research in these fields centers now on the functions and structure of the human genome – a set of chromosomes with the genes they contain which are directly involved in the mechanisms of heredity.

The problem became the focal point of scrutinity by scientists from a number of countries at a 1986 Santa Fe Conference. And even despite some differences the participants endorsed the draft of what was named the Human Genome Program

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which has evolved into a truly international effort undertaken jointly by scientists in the USA, Great Britain, France, Italy, Germany and Russia.

The road to comprehensive studies of the genome was paved by the progress of molecular biology over the past few decades. But as late as the middle of the 20th century genome remained but an abstract “unit” of heredity. Then after a chain of brilliant discoveries the abstract notion materialized into a tangible chemical structure.

The substance directly responsible for heredity is the often mentioned DNA, – an abbreviation which stands for deoxyribonucleic acid. This is a polymer consisting of four types of more simple low – molecular compounds called nucleotides which are distinguished from one another by four organic substances, or bases, which are

(A) adenine, (G) guanine, (C) cytosine or (T) thymine. They form extended thread – like structures – the chromosome.

The human genome consists of 23 pairs of chromosomes: 23 on the maternal and another 23 on the paternal side. The hub of each of them is a fine DNA thread in which one molecule consists of a chain of 50 to 250 nucleotides. The summary length of DNA within any of the 10 trillions of human body cells reaches 2 m. and it fits into a cell of not more then 20 micrones in diameter. And the nucleus as such within which it is confined has a much smaller diameter of about 5 micrones.

At this point one has to say a few words about the “language” carrying genetic information. Its alphabet consists of only four “letters” – the aforesaid four types of nucleotides. Genetic “texts” are recorded by different combinations of these letters and it is these “words” and “phrases” that contain the metabolic “commands” which control various vital processes. So one could say in a poetic manner that the objective of the Human Genome Project is to try and read “The Scroll of Human life”.

The priority task now is “the mapping of the genome”. Like an ordinary geographical map, a genome map will pinpoint the location of genes and other genetic clues on the chromosome.

The Human Genome Program deals with the causes of hereditary pathologies in man. Doctors are aware of a total of 4 thousand such disorders. This pathologic

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heredity cannot be ignored because it brings grief and suffering to families, the patients themselves and represent a considerable social problem. Pathologic heredity plays an essential role in a whole number of illnesses including diabetis, schizophrenia and arterosclerosis. What is more, most types of cancer are afflictions of the genome which start with its one single cell being damaged. The damaged cell becomes capable of unlimited multiplication, it inhibits the surrounding cells and continues to proliferate within the body, finally killing the patient.

Hereditary disorders are the result of an accumulation of harmful mutations. They occur in human population just as, probably, in any other. In 1950 the prominent American geneticist Dr. G. Miller issued a stern warning to the human race: because of genetic distortions homo sapiens is doomed to extinction as a species sooner or later. And although not all scientists share this pessimism, there is no denying such danger. Every one of us must carry within himself some pathological genes which can, in principle, either destroy or make us ill.

In Russia research under the Human Genome Program is chiefly related to bioinformatics as an indispensable part of studies of the human genome. Our researchers have developed analytical information – computer programs and are working on impoving the diagnostics of hereditary diseases. The Russian program enjoys widespread international recognition. But still our scientists are at the very beginning of this work. But there is every reason to regard current studies of the human genome as a main way leading biologists into the 21st century.

8.10 Exercise 10

Answer the following questions.

1)What is a human genome?

2)What countries take part in the Human Genome Program?

3)What substance is directly responsible for heredity?

4)What is the often mentioned DNA?

5)In what way are nucleotides distinguished from one another?

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6)What substances form the chromosomes?

7)How many pairs of chromosomes does the human genome consist of?

8)How does the DNA look like?

9)Describe the “language” carrying genetic information?

10)What does the Human Genome Program deal with?

11)Why did Dr. Miller issue his stern warning?

12)What researches do the Russian scientists make under the Human Genome Program?

8.11 Exercise 11

Fill in the sentences with suitable terms from the text.

1)…… is a polymer consisting of ……

2)…… are distinguished from one another by four ……

3)These organic substances form …… structures known as ……

4)The human …… consists of 23 pairs of …… 23 on the …… side and 23 on the …… side.

5)One molecule of DNA includes a chain of 50 to 250 ……

6)The alphabet of the language, carrying …… is made up of only four ……

7)A genome map will …… the location of ……

8)The Human Genome Program deals with ……

8.12 Exercise 12

Define if the following statements correspond to the text. Express your

agreement or disagreement with these statements.

1)The summary length of DNA within a human body cell reaches 10 meters.

2)A human body cell is not more than 20 micrones in diameter.

3)The nucleus within which DNA resides has much smaller diameter of about 40 micrones.

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4)The damaged cell inhibits the human genome.

5)The cell prolifirate within the body, killing a patient.

6)Our scientists deal with bioinformatics under the Human Genome Program.

7)They are working on the cancer cell structure.

8.13 Exercise 13

Fill in the schemes and speak about the DNA structure and human genome structure, figure 8.

DNA thread

nucleotides

chromosomes

Figure 8 - Exercise 13

8.14 Exercise 14

Find in the text the paragraph about the “language” carrying genetic information and translate it in written form.

8.15 Exercise 15

Find in the text the information about the Human Genome Problem. Discuss it with your partners: ask questions, share your opinions.

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8.16 Exercise 16

Find in the text the information about the hereditary disorders. Prepare your reports on them. Include if you can the additional information into your report.

8.17 Exercise 17

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

Of great importance for the concepts of modern genetics have been discoveries made in the latter half of the 20th century. It was then that the scientists came to the conclusion that DNA was the main store of genetic information, a “machine” for its reproduction. But it is proteins alone that can put this information to practical use. They are the direct molecular product of genome activity and from the point of view of molecular biologist they are the starting point in the formation of the genotype. It would be quite natural to assume that in heredity a great deal depends on the properties of DNA as such. Indeed, heredity embraces two opposite properties: stability and variability. The former is ensured by a whole number of biological mechanisms including the exactness (точность) of cell division, the exact replication of DNA, the presence of powerful reparatory (исправительная) system eliminating any or all mistakes in replication and also by selection at all levels of biological hierarchy (иерархия) from a cell to a whole population, when a living being confronts (противостоит) the external factors of Darwinist selection. As for variability, it is a most complicated and contradictory process. It is the result, above all, of mutations.

One of the most puzzling and obviously essential characteristics of DNA is what is called its excessiveness. It can be regarded as a manifestation of DNA variability. Since the immediate output (вещество) produced by DNA are proteins it would be only natural to assume that DNA must consist exclusively of proteins which control the synthesis. In fact this is what really takes place but in the most primitive

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of organisms. In higher ones from 3 to 5 percent of DNA is actually involved in protein synthesis and the mission of the remaining 95 to 97 percent remains obscure.

What we do know for sure is that excessive (чрезмерный) DNA is generated by the so – called recurrences. These are some bigger or smaller sections of DNA, monotonous (однородный) composition, scattered along the genome or concentrating in some areas of it, but each replicated many times over.

But the main characteristic of DNA appears to consist in its ability to self – replication. DNA molecules are the only ones in our body which contain everything necessary for self – reproduction. It was prompted (подсказывать) by excessive DNA whose formation depends on the replication properties of DNA – its ability to reproduce itself. Classical natural selection has no power over excessive DNA and cannot eliminate it. Only the surrounding cells can have some influence upon it.

But the problem of identification of any useful function of excessive DNA remains unresolved. At the fact that at least some kinds of excessive DNA do perform certain functions is supported by considerable evidence. In all probability excessive DNA provides for a degree of flexibility of the genome. Its biological function consists in offering readily available (легко доступный) raw material for building of new genes.

9 Texts for auding

9.1 The beginning of life

9.1.1 Exercise 1

Listen to the text and guess the meaning of the unknown words: spot, protozoa,

fin.

What were the first bits of living matter? They were very very small shapeless spots, called protozoa. Time went by and gradually one-celled organisms, called protozoa appeared. Gradually these organisms developed into fish having fins for swimming.

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9.1.2 Exercise 2

Listen to the text “The beginning of life” and write down as much information as possible.

Almost three-quarters of our body is water. In our blood scientists have found all the chemicals and minerals that make up seawater. They think that all life began in the waters of the sea.

Sunlight acted upon certain chemicals in the warm mud on the sea floor near the land. Lifeless chemicals joined together. They formed a new kind of molecule. These molecules had new powers: they could grow by taking food, and they could make other beings like themselves. Life has begun.

The first bits of living matter were tiny pieces of protoplasm. Protoplasm was in the form of tiny shapeless spots. After a long time those tiny spots of protoplasm began to change. One type began to make food by using the solar energy and developed into the first plants. Others lived by eating foodmakers. Another group could get food from plants or by eating other beings like themselves.

The protoplasm changed its form very many times. At last nearly 50 million years ago, after real life had begun, a new form of protoplasm appeared.

In the new form, only one part of protoplasm did the work of getting food. Another part, the nucleus, divided the protoplasm into two, forming a new being, a cell. With the first cell, modern life appeared, because all plants and animals are made up of cells from single-celled animals to man.

The sea gave birth to living matter. It also played a part in bringing many of the great changes in the form of life. And the sea has left us the story of later changes, written in stones. Scientists know the earliest forms of life because they study the simple forms of sea life today.

The sea had risen and fallen for billions of years before the first one-celled beings appeared. They were called protozoa.

Another long period went by, very many soft-bodied animals appeared in the sea; they tried to eat each other. Little by little, in the terrible struggle for life some of

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the soft-bodied animals developed hard shells (раковина) that lived in warm seas for 75 million years. Scientists find shells of died sea creatures between rock layers even today.

Later, a new kind of sea creatures appeared, the fish. It could swim, because of the fins it had.

Again the sea changed its level leaving lakes and swamps behind. Life in these swamps had to change or die out. Sea plants changed and some began to live in the open air. A few fish learned to get oxygen from the air and not from the water. They grew feet instead of fins. They could live on dry land and returned to the sea only to lay eggs and to raise their young. They were the first amphibians.

Then the sea began slowly to cover the edge of the land. Some amphibians returned to the sea, others learning to lay eggs and raise their young on dry land. They were reptiles from tiny lizard to dinosaur.

But in the swamps strange animals of a new kind appeared. They carried their young in their bodies and fed them with their own milk. Their bodies stayed at about the same temperature in cold and warm weather. They were the first mammals.

9.1.3 Exercise 3

Listen to the text for the second time and write down the sequence of appearing life on the earth.

9.1.4 Exercise 4

Arrange the points of the plan according to the text read.

1)The first single-celled beings were called protozoa.

2)Lifeless chemicals joined together and formed new molecules.

3)The first amphibians lived on dry land and returned to the sea to lay eggs and to raise their young.

4)One type of protoplasm began to make food by using the solar energy and developed into first plants.

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5)Others lived by eating foodmakers.

6)Soft-bodied animals appeared in the sea.

7)Another group of protoplasm got food from plants and ate other beings.

8)For 75 million years hard-shelled animals lived in the sea.

9)Strange animals of a new kind carrying their young in their bodies and feeding them with their own milk appeared. They were mammals.

10)A new kind of sea creatures, the fish, appeared.

9.1.5 Exercise 5

Answer the questions.

1)What substances make up sea water?

2)What was the result of sunlight action upon warm mud on the sea floor?

3)What is protoplasm?

4)In what way did protoplasm begin to change?

5)What did the appearance of life depend on?

9.1.6 Exercise 6.

Speak on the beginning of life in chain.

9.1.7 Exercise 7.

Speak on the same problem using the following clue words and expressions:

1)To make up sea water; lifeless chemicals; to grow by taking food; living matter; protoplasm; to use solar energy; to develop into the plants; to eat the foodmakers; to get food from plants; to eat other beings; to give birth.

2)One-celled beings; soft-bodied animals; to appear, a terrible struggle for life; hard-shelled animals; to get oxygen from the air; to lay eggs; to raise the young; to stay at the same temperature; mammals.

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