Программа «геном человека»: что это такое?

Основными задачами международного проекта "Геном человека" (Human Genome Project - HGP) являются секвенирование (sequencing)– то есть определение последовательности нуклеотидов суммарного набора молекул ДНК клетки человека и картирование (mapping) (идентификация генов и локализация места их расположения на хромосомах).

Идентифицировано множество генов, ответственных за многие болезни человека: онкологические, наследственные, нейродегенеративные, сердечно-сосудистые и пр. Поэтому полное выполнение программы «Геном человека» может кардинальным образом изменить здравоохранение. В последнее время активно прогрессирует медицинское приложение геномики - медицинская геномика, в частности, геномная диагностика. Ученые и врачи смогут больше узнать о происхождении конкретных заболеваний и о причинах предрасположенности тех или иных людей к этим заболеваниям. В свою очередь, фармацевтические и биотехнологические фирмы смогут намного быстрее и дешевле создавать новые лекарства, которые будут вызывать гораздо меньше побочных эффектов (например, аллергических реакций).

Геном человека, или совокупность всех его генов и межгенных участков ДНК, составляет более 3 млрд. нуклеотидных пар или пар оснований. Ранее эта величина казалась очень большой, и, учитывая прошлый уровень развития техники секвенирования и информационных систем обработки данных, предположения о прочтении генома человека выглядели фантастически. Тем не менее, в 1988 г. один из первооткрывателей знаменитой двойной спирали ДНК, лауреат Нобелевской премии Дж. Уотсон, публично высказал мысль о реальности возможности полного раскрытия нуклеотидной последовательности ДНК человека. В том же самом 1988 с аналогичной идеей выступил выдающийся российский молекулярный биолог и биохимик, академик А.А. Баев. Сначала эта идея была встречена весьма скептически. Критики считали, что решение данной задачи мало реально и нецелесообразно в научном отношении, к тому же потребует разорительных затрат. Однако время шло, и очень скоро научное сообщество во всем мире стало обсуждать ее всерьез.

Для координации национальных исследовательских программ возникла Международная организация по изучению генома человека (HUGO). Ученые шести стран мира (сейчас стран-участниц больше) договорились о работе с различными хромосомами и фрагментами генома человека и совместном определении полной структуры генома. На долю российских ученых пришлось исследование структур 3 и 19 хромосом человека. С самого начала работ по геномному проекту мир договорился об открытости, доступности всей получаемой информации для его участников независимо от их вклада и государственной принадлежности. Сейчас существуют общедоступные базы данных, в которых аккумулирована информация о структуре генома человека.

Unit 7

The Double Helix

Introduction

I. Listen to the text “Red Bread Mold Provided Insight into the Role of Genes”. Are these sentences true or false? Correct the false sentences.

1 Neurospora is very independent because it can synthesize the organic compounds it needs. T /F

2 Neurospora cannot grow on a minimal medium. T / F

3Neurospora has just one copy of each gene that is why it is very useful in experiments. T / F

4 George Beadle and Edward Tatum wanted to see the DNA of Neurospora with the help of X-ray diffraction. T / F

5The mutations caused by X-rays caused Neurospora to need more nutrients. T / F

6 The experiment of Beadle and Tatum proved that each enzyme is encoded by one gene. T / F

7 The experimental mutant mold could not grow unless citrulline was added to the medium. T / F

8 The experimental mutant mold lacked many enzymes. T / F

II. Are the following definitions correct? Change the wrong ones.

a A gene is a functional segment of DNA located at a particular place of a chromosome.

b Nucleic acid consists of four very similar subunits called nucleotides.

c Each nucleotide of DNA consists of three parts: a phosphate group, deoxyribose and a nitrogen-containing base that has a single-ringed structure.

d Chromosomes are long strands of DNA which are in eukaryotes complexed with lipids.

e Replication is a process of copying DNA to produce two identical DNA double helices.

f In transcription, the information contained in the whole of the DNA is copied into messenger RNA (mRNA).

g In translation, transfer RNA (tRNA) and ribosomal RNA (rRNA) convert the information of the base sequence in messenger RNA into a specific amino acid sequence and so help synthesize the protein.

Reading

Read the text. The exercise after the text will help you with the new words.

The Discovery of the Double Helix

I

In the early 1950s, many biologists realized that the key to understanding inheritance lay in the structure of DNA. They also knew that whoever deduced the correct structure of DNA would receive recognition from fellow biologists, fame in the popular press, and very possibly the Nobel Prize. Less obvious were the best methods to employ and who would be the person to do it.

II

The betting favorite in the race to discover the structure of DNA had to be Linus Pauling of Caltech. Pauling probably knew more about the chemistry of large organic molecules than did any person alive, and he had realized that accurate models could aid in deducing molecular structure. Like Rosalind Franklin and Maurice Wilkins, Pauling was an expert in X-ray diffraction techniques. Finally, he was almost frighteningly brilliant. In 1950s, he demonstrated these traits by showing that many proteins were coiled into single-stranded helices. Pauling, however, had two main handicaps. First, for years he had concentrated on protein research, and therefore he had little data about DNA. Second, he was active in the peace movement. During the early 1950s, some government officials, including Senator Joseph MrCarthy, considered such activity to be potentially subversive and possibly dangerous to national security.

III

The second most likely competitors were Wilkins and Franklin, the English scientists who had set out to determine the structure of DNA by the most direct procedure, namely the careful study of the X-ray diffraction patterns of DNA. They were the only scientists who had very good data about the general shape of the DNA molecule. Unfortunately for them, their methodical approach was also slow.

IV

The door was open for the eventual discoverers of the double helix, James Watson and Francis Crick, two young scientists (American and English, respectively) with neither Pauling’s tremendous understanding of chemical bonds nor Franklin and Wilkins’s expertise in X-ray analysis. They did have three crucial advantages: (1) the knowledge that models could be enormously helpful in studying molecular structure, a lesson learned from Pauling’s work on proteins; (2) access to the X-ray data; and (3) a driving ambition to be first.

V

Watson and Crick did no experiments in the ordinary sense of the word; rather, they spent their time thinking about DNA, trying to construct a molecular model that made sense and fit the data. Because they were based in England and because Wilkins was very open about his and Franklin’s data, Watson and Crick were familiar with all the X-ray information relating to DNA. This information was just what Pauling lacked. Because of Pauling presumed subversive tendencies, the U.S. State Department refused to issue him a passport to leave the United States, so he could neither attend meetings at which Wilkins presented the X-ray data nor visit England to talk with Franklin and Wilkins directly.

VI

Watson and Crick knew that Pauling was working on DNA structure and were terrified that he would beat them to it. In his book ‘The Double Helix’, Watson recounts his belief that, if Pauling could have seen the X-ray pictures, “in a week at most, Linus would have the structure.”

VII

You might be thinking now, “But wait just a minute! That’s not fair. If the goal of science is to advance knowledge, then everyone should have access to all the data. If Pauling was the best, he should have discovered the double helix first.” Perhaps so. But science is an activity of scientists who, after all, are people too. Although virtually all scientists want to see the advancement and benefit of humanity, each individual also wants to be the one responsible for that advancement and to receive the credit and the glory. The ambition to be first helps inspire the intense concentration, the sleepless nights, and the long days in the laboratory that ultimately produce results.

VIII

Linus Pauling remained in the dark about the correct X-ray pictures of DNA and was beaten to the correct structure. When Watson and Crick discovered the base-pairing rule that was the key to DNA structure, Watson wrote a letter about it to Max Delbruck, a friend and advisor at Caltech. He asked Delbruck not to reveal the contents of the letter to Pauling until their structure was formally published. Delbruck, perhaps more of a model scientist, firmly believed that scientific discoveries belong to the public domain and promptly told Pauling all about it. With the class of a great scientist and a great person, Pauling graciously congratulated Watson and Crick on their brilliant solution of the DNA structure. The race was over.

Words, Words, Words

I. In paragraphs I-VIII of the text find words meaning the following:

praise, respect or admiration (I) ………

the person or animal who is expected to win the competition (II) ………

correct or true in every detail (II) ………

very intelligent (II) ………

a disadvantage that prevents you from doing something well (II) ………

intended to destroy the power of the government (II) ………

to start working in order to achieve an aim (III) ………

in the order in which they were mentioned (IV) ………

special skill or knowledge that you get from experience, training or studying (IV) ………

to do something before someone else (VI) ………

to say what happened (VI) ………

praise for something you have done or achieved (VII) ………

after a process or activity has ended (VII) ………

to make known (something secret or hidden) (VIII) ………

II. As you learned from “The Discovery of the Double Helix”, scientists in different laboratories often compete with one another to make new discoveries. Do you think this competition helps to promote scientific discoveries? Sometimes, researchers in different laboratories collaborate with one another. What advantages does collaboration offer over competition? What factors might provide barriers to collaboration and lead to competition?

Advantages of Collaboration:   1.   2.   3.	Advantages of Competition:   1.   2.   3.
Factors providing barriers to collaboration and leading to competition: 1.   2.

Language focus 1

Modal Auxiliary Verbs: Overview

Modal auxiliary (“helper”) verbs are: can, could, may, might, will, would, shall, should, must and ought to. Sometimes verbs be, dare, have and need act as modal verbs, too.

Modal verbs

a) do not add –s in the third person singular;

b) form questions, negatives, question tags and short answers without do;

c) need an infinitive without to after them (except for be to, need to, ought to);

d) do not have infinitives or participles (to may, maying, musted);

e) can be followed by perfect or continuous infinitives (must have been, could be doing, etc.) to express ideas of past or progressive;

f) have contracted forms (can’t, won’t, ‘d (for would), ‘ll (for will), etc.).

Modal auxiliary verbs have many meanings. Among them are: 1) ability 2) obligation to do something, 3) permission, 4) degrees of certainty, 5) conditional meaning.

I. Determine the meaning of the modal verb in each of the sentences.

1. Can swim ten lengths of the swimming pool without stopping.

2. You should be more attentive during the test: you can make 5 mistakes in one word!

3. You are a princess and you must never say such words!

4. May I come in?

5. He might have missed the last train and is now stranded at the station.

6. How could I be such a fool?

7. That must have been a mistake!

8. You can borrow my car, if you want.

9. If I hadn’t been such a snob I might have stayed with my parents.

10. The text can’t be so small! It is just an introduction.

II. Work with a partner. Use the phrases below in situations of your own:

1. He might have seen you wrapping it!

2. How long must I stand here like a statue?

3. You should do it as quickly as you can.

4. Can you show me the way?

Language focus 2

Can and Could: Ability

To express the notion of ability, modal verbs can/could are used in English. The meaning of ability is the primary meaning of these verbs. For example:

I can read Italian, but I can’t speak it.

Can gases freeze?

When I was 5 years old, I could swim two lengths of the swimming pool. My friends couldn’t swim so far.

However, we can not use these two verbs in every tense. That is why the expression to be able to is used in other tenses:

Present: I can climb trees. – I am able to climb trees. (No difference in meaning, can sounds better.)

Past: I could draw people when I was 5. = I was able to draw people when I was 5. (General ability.) BUT: I was able to draw that man (was able to = managed to, succeeded in)

Future: You’ll be able to walk soon. (Only one form is used for future abilities.)

Infinitive: I like to be able to run fast. (Can is not used in the infinitive.)

Perfect: I’ve always been able to play games well. (Can is not used in the perfect.)

Gerund: Being able to practice parachute-jumping is very important for me. (Can is not used in the –ing form.)

Participle: Being able to collect a lot of money by singing, he decided to do so.

I. Interview your group-mates and find the person who:

(name)

a) was able to read when he was three ………….…………………………….

(Ask everybody: Were you able to read when you were 3?)

b) can drive a car …………….………………………..……….

c) has always been able to fight well ……….………………………………..…….

d) will be able to visit Europe in summer …………………….………………….

e) could watch horror movies when he was five .………………………..……….

II. Write in your notebook five words or expressions on the following in random order.

1. Something you used to be able to do but can’t do now.

2. Something you would like to be able to do in the future.

3. Something that you like being able to do.

4. Something you’ve been able to do this week.

5. Something you’ll be able to do when you graduate from the University.

Now swap your notes with your partner and ask questions looking at his/her notes. (For example: Did you use to be able to play the piano well?)

III. Read the following dialogue. Who is speaking? Finish the dialogue. Act similar dialogues in class, changing the names and other information.

- Hello, Mr. Parker. I am John Stevens.

- Hello, Mr. Stevens. So, you are applying for the position of …

- Of a photographer. I can write small articles to the photographs as well.

- Good. We’re always in a hurry here. Are you able to act quickly and efficiently?

- Yes, I am. In my previous job I was able to act very quickly.

- What did you do?

- I… er… was a scuba diving photographer. When you dive, you know, you must be very attentive and make decisions quickly. I was able to get away from that shark… and even save my camera.

- Oh!..

- I can also climb mountains, sail a boat, and fly a small airplane…

- That will do, thank you. Can you develop films?

- Oh yes, sir.

- Our magazine is a comic one. So we need comic photographs. Can you make comic photographs? …

Can or Will Be Able to

We use can to talk about future actions which we will be able to do because of present ability, present circumstances, present decision, etc. Will be able to is used specially to indicate future ability to do something.

IV. Fill in the gaps with can or will be able to.

1. I …………. give you a hand with this work, if you like.

2. I …………. solve this problem in an hour or two.

3. I …………. explain it to you once again.

4. I …………. lend you my notebook for a few days, to prepare for the test.

5. I …………. spend more time with my husband when I leave the university.

Language focus 3

Ability: Could Have Done

1 Could have done is a special structure to talk about unrealized past ability or opportunities – to say that somebody was able to do something, but did not try to do it; or that something was possible, but did not happen.

I could have married anybody I wanted to. (Unrealized past ability.)

That was a bad place to go skiing – you could have broken your leg. (It was possible, but it didn’t happen.)

I couldn’t have won, so I didn’t go in for the race. (In negatives – inability in the past.)

NB: I couldn’t win the race. (It is uncertain whether I took part in it.)

I couldn’t have won the race even if I had tried. (I did not take part in the race at all.)

2 Sometimes could have done is used to criticize actions:

You could have helped me – why did you just sit and watch?! (Criticism of a past action.)

3 The same forms are used in past and present conditionals:

I could have given up all research, if I hadn’t met that professor. (Unrealized condition in the past.)

I could give up all research, if I was not interested in it. (Unrealized condition in the present.)

These forms exist in both active and passive voice:

	Active	Passive
Present	could do	could be done
Past	сould have done	could have been done

I. Put the verb in brackets into the correct form.

1. You could (kill) the bird! You were not careful when you took it!

2. You could (listen) to what I am saying.

3. The book could (read) more attentively if everything had been explained beforehand.

4. The work could (do) with more precision if the techniques we used had been more accurate.

5. You could (eat) first and (play) after.

6. I could (be) in prison now if not for you.

7. That could (be) an ideal solution if we didn’t know of the existence of that factor.

8. The experiment could (conduct) with due care if the second laboratory assistant was present.

9. The event could (place) into the list of the most wonderful discoveries in world history if it had been known to anybody but the scientist who died the next day.

10. I could (produce) a better impression! But I began to worry long before I saw the employer and couldn’t (do) better.

II. Use the following word combinations in phrases of your own.

1. … could possibly revise …

2. … can’t determine …

3. I can replace …

4. … couldn’t have decided …

5. … was able to calculate …

6. …could have counted …

7. … could have been achieved if …

8. I could try ……..

Language focus 4

Uncertainty, Doubt, Improbability

1 Can it be true? Неужели это правда?

Could (more uncertain)

Can/ Could she be telling lies? (The continuous infinitive is used)

Can/Could she have said it? (To show that something happened in the past use the perfect infinitive)

Can/Could she really have been waiting for us so long? (The action began in the past and continues into the present)

2 It can’t be true Не может быть, чтобы это было правдой!

couldn’t

He can’t be telling lies!

couldn’t

He can’t have said this! (Something happened in the past)

couldn’t

She can’t/couldn’t have been waiting for us so long! (The action began in the past and continues into the present.)

I. Substitute an English verb in the correct form for the Russian one in the brackets.

1. He can’t (сказал) that to your mother!

2. Can it (происходит) every day in our faculty?

3. Could he (работал и до сих пор работает) in this strange organization?

4. We couldn’t (видели) this so many times!

5. You can’t (смотришь) at these things and not (делаешь) anything with that!

6. Could you (ждал) so long?

7. They couldn’t (были) there.

II. Use two or more of the phrases from I in situations of your own.

III. Translate into English.

1. Не может быть, чтобы он это написал!

2. Ты мог бы переписать дискету, пока был у меня дома.

3. Вы не могли бы подержать мою сумку?

4. Он умел плавать в три года!

5. Она смогла только подняться с постели и сделать три шага.

6. Можно мне взять твою расческу?

7. Разве такое может случиться в нашей семье?

8. Неужели вы столько лет исследуете одну только плесень?

9. Он мог отдать вам все материалы и больше никогда не вспомнить об этом, но он этого не сделал.

10. Ты мог бы сейчас загорать где-нибудь в Испании…

11. Из нашего окна можно увидеть только каменную стену и маленький кусочек голубого неба.

12. Разве он до сих пор проводит подобные эксперименты?

13. Не может быть, чтобы новое средство не подействовало! Мы его опробовали, и оно дало хороший результат.

14. Разве вы не искали меня?

15. Ты не мог бы быть внимательнее, когда решаешь такие сложные задачи?

16. Эту книгу можно купить в любом магазине.

Render in English.

Образование и-РНК по матрице ДНК

Биосинтез белков идет в каждой живой клетке. Наиболее активен он в молодых растущих клетках, где синтезируются все виды белков. Основная роль в определении структуры белков принадлежит ДНК. Участок молекулы ДНК, содержащий информацию о структуре одного белка, называют геном. Поэтому информацию, которая содержит ДНК, называют генетической.

Информация, содержащаяся в ДНК, переписывается на и-РНК. Этот процесс называют транскрипцией. Специальный фермент – РНК-полимераза, двигаясь по ДНК, подбирает по принципу комплементарности нуклеотиды и соединяет их в единую цепочку. Если в нити ДНК стоит тимин, то полимераза включает в цепь и-РНК аденин, если гуанин – включает цитозин, если аденин – то урацил (в состав РНК не входит тимин).

По длине каждая из молекул и-РНК в сотни раз короче ДНК. Информационная РНК – копия не всей молекулы ДНК, а только части ее, одного гена или группы рядом лежащих генов, несущих информацию о структуре белков, необходимых для выполнения одной функции.

В начале каждой группы генов находится своего рода посадочная площадка для полимеразы. Только присоединившись к ней, полимераза способна начать синтез и-РНК. В конце группы генов фермент встречает сигнал (в виде определенной последовательности нуклеотидов), означающий конец переписывания. Готовая и-РНК отходит от ДНК, покидает ядро и направляется к месту синтеза белков – рибосоме, расположенной в цитоплазме клетки.

В клетке генетическая информация передается только от ДНК к белку.

Unit 8

Inheritance

Introduction

Read the following passage and listen to the story about Gregor Mendel’s life. Find six false facts in the story you hear.

Before settling down as a monk in the monastery of St. Thomas in Brünn (now Brno, in the Czech Republic), Gregor Mendel tried his hand at several pursuits, including health care and teaching. To earn his teaching certificate, Mendel attended the University of Vienna for 2 years, where he studied botany and mathematics, among other subjects. This training proved crucial to his later experiments, which were the foundation for the modern science of genetics. At St. Thomas in the mid-1800s, Mendel carried out both his monastic duties and a groundbreaking series of experiments on inheritance in the common edible pea. Although Mendel worked without knowledge of genes or chromosomes, we can more easily follow his experiments after a brief look at some modern genetic concepts.

Reading

I. Read the extract from a textbook and write out all the terms relevant to the topic of the unit and their definitions contained in the text.

A gene’s specific physical location on a chromosome is called a locus (plural, ‘loci’). Homologous chromosomes carry the same genes, located at the same loci. Although the nucleotide sequence at a given gene locus is always similar on homologous chromosomes, it may not be identical. These differences allow different nucleotide sequences at the same gene locus on two homologous chromosomes to produce alternate forms of the gene, called alleles. Human A, B, and O blood types, for example, are produced by three alleles of the same gene.

If both homologous chromosomes in an organism have the same allele at a given gene locus, the organism is said to be homozygous at that gene locus. (“Homozygous” comes from Greek words meaning “same pair”.) If two homologous chromosomes have different alleles at a given gene locus the organism is heterozygous (“different pair”) at that locus and is called a hybrid. During meiosis, homologous chromosomes are separated, so each gamete receives one member of each pair of homologous chromosomes. Therefore, all the gametes produced by an organism that is homozygous at a particular gene locus will contain the same allele. Gametes produced by an organism that is heterozygous at the same gene locus are of two kinds: half of the gametes contain one allele, and half contain the other. (…)

Mendel’s choice of the edible pea as an experimental subject was critical to the success of his experiments. In plants, a male gamete, which for simplicity we’ll call the sperm, is contained in each pollen grain. The structure of the pea flower normally prevents another flower’s pollen from entering. Instead, each pea flower normally supplies its own pollen, so the egg cells in each flower are fertilized by sperm from the pollen of the same flower. This process is called self-fertilization. Even in Mendel’s time, commercial seed dealers sold many types of peas that were true-breeding. In true-breeding plants, all the offspring produced through self-fertilization are homozygous for a given trait and are essentially identical to the parent plant.

Although peas normally self-fertilize, plant breeders can also mate plants by hand, a process called cross-fertilization. Breeders pull apart the petals and remove the stamens, preventing self-fertilization. By dusting the carpels with pollen they have selected, breeders can control cross-fertilization. In this way, two true-breeding plants can be mated to see what types of offspring they produce.

In contrast to earlier scientists, Mendel chose to study traits – heritable characteristics – that are unmistakably different forms, such as white flowers versus purple flowers, and he worked with one trait at a time. These factors allowed Mendel to see through to the underlying principles of inheritance. Equally important was the fact that Mendel counted the numbers of offspring with each type of trait and analyzed the numbers. The use of statistics as a tool to verify the validity of results has since become an extremely important practice in biology.

II. Add to the list of terms the following and write their definitions in English.

first-generation offspring

second-generation offspring

parental generation

Mendel’s law of segregation

dominant allele

recessive allele

genotype

phenotype

the Punnett square method (by R.C.Punnett)

test cross

linkage

crossing over

III. In certain cattle, hair colour can be red (homozygous RR), white (homozygous R’R’), or roan (a mixture of red and white hairs, heterozygous RR’).

a. When a red bull is mated to a white cow, what genotypes and phenotypes of offspring could be obtained?

b. If one of the offspring in (a) were mated to a white cow, what genotypes and phenotypes of offspring could be produced? In what proportion?

Explain the solution of the problems in English.

Language focus 1

May and Might: Possibility and Degrees of Certainty

1 May and might are used mainly to express the uncertainty of something happening, and to ask for and give permission.

I may see you tomorrow. (Perhaps a 50% chance)

Peter might phone. (Perhaps, a 30% chance). If he does, ask him to ring later.

Do you think I might borrow your typewriter? (Permission, very polite)

In the majority of cases might is not the past form of may!

I felt very hot and tired. Perhaps I was ill. (NOT …I might be ill.)

2 Uncertainty in the past – use might have done:

What was that noise? – It might have been a cat (we don’t know and just guess)

Chances in the present or future with by:

I’ll try phoning him, but he may have gone out by now. (present)

By the end of this year I might have saved some money. (future)

3 Something was possible but did not happen – use might have done or could have done:

If she hadn’t been so bad-tempered, I might/could have married her .

4 In scientific and academic language, may is often used to talk about typical occurrences – things that can happen in certain situations.

A female crocodile may/can lay 30-40 eggs. (can is less formal)

The flowers may have five or six petals, pink or red on colour.

With this meaning might can be used to talk about the past:

In those days, a man might/could be hanged for stealing a sheep. (could is less formal)

May and Might: Degrees of Certainty

He may (might) (not) be at home. Может быть (возможно), он (не) дома.

(might is more uncertain)

He may (might) come soon. Может быть (возможно), он скоро придет.

He may (might) be reading now. Может быть (возможно), он сейчас читает.

He may (might) have come already. Может быть (возможно), он уже пришел.

He may (might) have been waiting for us for an hour. Может быть (возможно), он ждет нас уже час.

I. Say what the meaning of may (might) isin the following sentences:

1. I have found a screwdriver! That may work!

2. Might I possibly see the director?

3. You may not be late for the meeting.

4. You might have come home earlier. We were waiting for you to have dinner.

5. He might be killed on the street if he had taken part in the demonstration of protest.

6. They might need your help. Ask them if you could help with anything.

7. You might listen to me more attentively.

8. May I use your telephone, please?

9. I may go to Austria on holidays.

10. They were told they might see the boy if they wore special clothes.

II. Fill in the gaps with the most appropriate form of the infinitive.

1. The students might ……………… (wait) for half an hour already for the lecture to begin, but the professor is still talking to another professor who does not have a lecture at the moment.

2. Look! He may …………….. (come) already. There is no one in the hall.

3. It may …………….(rain) today. The clouds are so dark.

4. She might …………….. (be) at home, so call her and ask. I will give you her telephone number.

5. I might ……………. (not lose) my temper when I speak to her, I don’t know.

6. They may ………………. (tell) him everything about me. What will he think of me?!

7. I don’t let her know my secret because she may ……………… (tell) everybody.

8. Look! It may ………………….. (rain) for several hours. The roads are so wet.

9. Mum might ………………….. (talk) to her friend. She’s been in the other room for an hour. Or she might ………………… (go) out.

III. Translate into English.

1. Возможно, вчера еще были лекции, но я остался дома.

2. Может быть, он пошел к врачу. Я сегодня не видела его на занятиях.

3. Может, он гуляет сейчас где-то со своими знакомыми, но я не уверена.

4. Он может уехать в любой день, так что свяжись с ним сегодня.

5. Возможно, я не приду завтра. Что-то я плохо себя чувствую.

6. Он, возможно, уже два часа спит. Надо его будить.

7. Я, может, и соглашусь, но только когда узнаю все условия.

8. Мы могли бы подождать тебя. Иди и поговори с ним, пока он здесь.

9. Он, возможно, ждет твоего звонка. Позвони ему!

10. Быть может, он не сможет сегодня навестить тебя. Не расстраивайся.

IV. Make up situations of your own using one or several of the following sentences:

1. May I see your hand?

2. You might have been cleverer!

3. I may close my eyes and jump if you want.

4. They might have chosen the wrong one, if not for me!

5. Might I possibly see the one you’re holding?

Language focus 2

Permission, Offer

1 Several forms are used to ask for and give permission to do things. These forms differ in formality, or politeness.

Most used and not very formal:

Can I borrow your car, Dad? – Sorry, you can’t. I am going to need it soon.

Could I ask for something? – Yes, of course, you can.

Could I possibly ask for something? – Sure, please do.

Do you think I could borrow your bike? – OK, but be careful.

More formal/polite:

May I take this book home, please? – No, you may not. It is for library use only.

Might I possibly borrow your pen for a moment, Professor? – Please do.

Do you mind if I smoke in here? – Sorry, it is a non-smoking area.

I wonder if I could possibly have something to eat. – Make yourself at home!

2 When you offer to do things, you may sound more or less definite.

I’llget you a taxi. – Thanks! (more definite)

Can I carry your bag? – Oh, thank you.

Would you like to have a cup of coffee? – Yes, that would be very nice.

I could mend your bicycle for you, if that would help. (less definite)

I. Fill in the gaps with a suitable word or expression.

a) - Could I ……………… borrow your textbook till tomorrow?

- Sorry, you ……………. . I’ve not yet done the home task.

b) …………………………. if I take a look at your notes?

- Please …………….. . Always welcome.

c) (on the phone) - May I speak to Professor Snow, ………………?

- Sorry, he is now at the meeting. Will you leave a message for him?

d) Do ……………………. I could go to that party with you?

- Well, I think everybody would be just happy if you did.

e) - …………………… if we could go out tonight.

- Oh, I think it is a good idea.

II. Choose the characters and situation and prepare a dialogue using at least two of the expressions from exercise I.

A father and a daughter A customer and a shop assistant A customs officer and a smuggler A police officer and a hippie A secretary and a visitor A doctor and a patient

III. Think of situations where the following sentences could be said. Act out the situations

1. Would you like a brown or a yellow one?

2. I think I could handle it for you.

3. I’ll send you one.

4. Can I help you out?

Words, Words, Words

I. First, fill in the gaps in the extract with appropriate words. Second, after checking the words formulate with your partner five true statements and five false statements based on the text. Read them to another pair so that they determine which ones are true/false.

Sex-Linked Genes are Found Only on the X or Only on the Y Chromosome

Genes that are on one _______ chromosome but not on the other are said to be sex-linked, or X-linked. In many animals, the Y chromosome carries relatively few genes other than those that determine _______, whereas the X chromosome bears many _______ that have nothing to do with specifically female traits. The human X-chromosome, for example, contains genes for colour vision, _______ clotting, and certain structural proteins in muscles that have no counterpart on the Y chromosome. Therefore, because they have two X-chromosomes, _______ can be either homozygous or _______ for genes on the X chromosome. Normal _______ versus recessive relationships among alleles will be expressed. _______, in contrast, most fully express all alleles they have on their single X chromosome, whether those _______ are dominant or recessive. For this reason, in humans, most cases of colour _______, hemophilia, and certain types of muscular dystrophy occur in males.

How does the sex linkage affect inheritance? Let’s look at the first example of sex linkage to be discovered, the inheritance of eye color in the fruit _______ Drosophila. Because these flies are small, have a rapid reproductive rate, and have few chromosomes, _______ have been favoured subjects for genetic studies for more than a century. Normally, Drosophila have red eyes. In the early 1900s, researchers in the laboratory of Thomas Hunt Morgan at Columbia University discovered a male fly with _______ eyes. This white-eyed male was mated to a virgin, true-_______ red-eyed female. All the resulting offspring were red-eyed flies, suggesting that white colour ( r ) is _______ to red ( R ). The second generation, however, was a surprise: there were nearly equal numbers of red-eyed males and white-eyed males but no females with white eyes! A test cross of the first-generation red-eyed females and the original white-eyed male yielded roughly equal numbers of _______ and white-eyed males and females.

II. From the data above, could you explain the case?

Language focus 3

May and Can

1 these two verbs can both express possibility due to circumstances:

He may find the book at the library = He can find the book at the library. (present or future)

But in questions and negatives only can is used.

Might in this meaning does not express past. It is found only in reported speech.

He said you might find the book at the library.

Could, however, expresses a past action.

He could find the book at the library yesterday.

2 asking for permission, we use both can and may but may is more formal:

May (might = more formal) I speak to you for a moment, professor?

Can (could) I have a cup of tea, Mum?

3 for uncertainty in affirmative sentences, use only may (might = more uncertain):

He might have gone home, if he’s not here.

4 for uncertainty in questions, use only can (could = more uncertain):

Could he have said that?

5 to say that you don’t believe something is true, use can’t or couldn’t (more uncertain):

He simply can’t have said that!

I. Add one sentence to each of the ones given here to clarify the situation they are used in.

1. You might have come earlier!

2. They could have called me.

3. He can sing and dance.

4. I may go to the Urals on holiday.

5. Can it be true?

6. Could he have said that?

7. You may go.

8. You might decide now!

9. He might be at home.

10. They could have been waiting for us for half an hour.

11. They can’t have done that!

12. Could I come tomorrow?

13. You could be more attentive.

14. How could you say that?

15. He may have been here for two hours, waiting.

II. Translate into English.

1. Может быть, наша группа и собиралась вчера, но я об этом не знаю.

2. Мы могли бы увидеться завтра, часов в пять.

3. Не может быть, чтобы ты это написал!

4. Можно, я возьму свои книги?

5. Он может и сообщить заведующему кафедрой обо всем.

6. Разве сейчас у другой группы идет лекция?

7. Он смог достать эту книгу в одном маленьком магазинчике.

8. Неужели вы уже все написали!

9. Может быть, мы всю жизнь его ждали.

10. Не может быть, чтобы мы всю жизнь ждали его.

11. Он мог там быть в двенадцать. Я не знаю, был ли он там.

12. Ты сможешь зайти ко мне завтра?

13. Разве она сможет сделать это?

Words, Words, Words

I. Fill in the gaps with appropriate modal verbs.

A DNA Probe ___ be Used to Locate the Gene within the DNA Library

Researchers find genes of interest by using DNA probes, sequences of nucleotides that are complementary to those genes. DNA probes are generated in specific ways. For example, if you know the amino acid sequence of the protein encoded by a gene, you ___ work backward through the genetic code to determine the corresponding DNA nucleotide sequences. Researchers synthesize a complementary copy of the nucleotide sequence for all or part of the gene, incorporating a marker such as radioactivity. This synthetic sequence ___ then be used to identify bacteria from the DNA library that contain a plasmid with the gene in question.

Messenger RNA ___ also be used as a DNA probe. Immature red blood cells, for example, synthesize lots of hemoglobin, so mRNA for hemoglobin ___ easily be extracted from them. This mRNA is complementary to the DNA of the hemoglobin gene and ___ be labeled and used as a DNA probe to locate the plasmid-containing bacteria. The amino acid sequences for many human hormones are known; these sequences ___ be used to create DNA probes for the genes for human hormones.

Once mRNA for the desired gene is obtained, it ___ also be used to generate the corresponding complementary strand of DNA (cDNA) by using a viral enzyme called reverse transcriptase. Geneticists ___ then use the cDNA as a DNA probe to identify the bacterium that contains the appropriate plasmid. The cDNA ___ instead serve as a template for generating double-stranded DNA, which ___ then be copied (…).

After checking the modal verbs look through parts of sentences below describing the synthetic sequence that can be used to identify bacteria from the DNA library. Match parts of the sentences and translate the resulting text into both Russian and English.

1Bacteria from the DNA library are sparsely distributed over a culture…   2 Each bacterium multiplies into a visible bacterial population (called a colony)… 3 A sheet of special filter paper is pressed… 4 It picks up a few bacteria from each colony,…     5The original culture dish… 6 The filter paper is placed in a basic solution, breaking open the bacteria, freeing the plasmids, and… 7 The paper is bathed in solution of neutral pH that contains a DNA probe (yellow),… 8 The probe hydrogen-bonds only to plasmid DNA that is complementary to the nucleotide sequence of the probe and… 9The locations of radioactivity on the paper are matched to the… 10Colonies in the same position consist of… 11 Samples of these bacteria are now cultured in new…

A …последовательность нуклеотидов, комплементарных нужному гену. B …на чашку для культивирования.   C …чашках, воспроизводя нужный ген. D …местоположением бактериальных колоний на первоначальной чашке для культивирования. E …содержащей питательную среду. F …содержащую единичный тип комбинации «плазмида – ДНК человека». G …бактерий, содержащих плазмиды с нужным геном.   H …разделяя двунитевую ДНК плазмид на одиночные нити.   I …следовательно, содержит человеческий ген.   J …остается в сохранности.   K …сохраняя позиции колонии.

II. Choose the correct modal verb.

Most Human Genetic Disorders are Caused by Recessive Alleles

The human body depends on the integrated actions of thousands of enzymes and other proteins. A mutation in the gene coding for one of these enzymes almost always impairs or destroys enzyme function. However, the presence of one normal allele (could/may) generate enough functional enzyme or other protein that heterozygotes with a defective allele are phenotypically indistinguishable from homozygous normals. Therefore, most normal alleles are inherited as dominant traits and mutant alleles as recessive traits. In other words, both alleles (must/can) be defective for the problem to show up in the offspring.

Heterozygous carriers are phenotypically normal but (can/may) pass on their defective recessive allele to their offspring. Although many people are carriers of a serious genetic defect, an unrelated man and woman who marry are unlikely to possess the same defective allele and to produce a homozygous child with the disorder. Related couples, however (especially first cousins or closer), have inherited some of their genes from recent common ancestors. Therefore, they are much more likely to carry the same defective allele and, if they bear children, to pass on the defect.

III. Eugenics is a term applied to the notion that the human condition might be improved by improving the human genome. Do you think there are both good and bad sides to eugenics? What examples can you think of to back up your stand? What would a eugenicist think of the medical advances that have ameliorated the problems of hemophilia?

IV. Using the data that follow, give a brief description of some genetic diseases.