Make a plane of the text.

Choose one of your group mates and ask him about genetic engineering. Give him a mark.

Cloning

1. Read the text and write all words to be important:

The news from Scotland arrived like a thunderstorm. The birth of Dolly, the sheep grown from an egg cell whose nucleus had been replaced with DNA from the mammary tissue of a six-year-old ewe, became known to the whole world. Cloning was at hand. Then ABS Global, Inc., a small company specializing in reproductive services in De Forest, Wisconsin, announced that ten Holstein cows cloned from differentiated cells, would soon be born.

The general public responded immediately after the first publication appeared. "Parade", the American Sunday news­paper supplement, asked several teenagers to speak about human cloning. "You can clone every part of a human body," said one 18-year-old. "So people will be cloned, but you won't know who the clones are walking down the street — and how do you know if they're going to have a soul?" Cloning, as the teenager's reaction shows, interferes with human insecurities about personal identity. Public attitudes about human cloning, of course, are both formed by the movies and reflected in them. After 70 years of watching humans being duplicated on-screen, moviegoers are in a special position to answer the question: What do we really think about cloning?

Nevertheless, the prospects for cloning are largely posi­tive. Cloning will make it easier and safer to find acceptable donor organs for people who need transplants.

The benefits of cloning a prize steer are clearly under­stood by farmers. Cloning could make transgenics — the transfer of human genes into animal cells — an economic reality. But the defects of monoculture that have already been observed in cloned crops would surely also apply to cloned animals.

For science itself, the cloning of Dolly is only the latest success in the research that began a few decades ago with an attempt to answer one of the central puzzles in developmen­tal biology: How does the fertilized egg give rise to so many different kinds of cells?

2. Find in text the English for the following words and phrases:

материнская ткань; клонирование; клонировать; выделенные клетки; отреагировать; клонирование чело­века; душа; внедряться в; опасения; отличительная черта личности; отношение общественности к чему-либо; упрощать что-либо; попытка; загадка; оплодотворенная яйцеклетка.

3. Using text (and your dictionary), complete the list of
definitions:

to clone  — to create an animal or plant in a laboratory from the animal's or plant's DNA.

clone  — an exact copy of an animal or plant created in a laboratory from the animal's or plant's DNA.

to transplant  —

transplantation  —

transfer  —

to transfer  —

transgenic  —

 

4. Answer the questions:

1) How was Dolly grown?

2) What did the ABS Global announce?

3) How soon did the general public respond to the news?

4) What did the teenager tell the "Parade" journalist?

5) What does the teenager's reaction show?

6) How are public attitudes about human cloning formed?

7) Why are the prospects for cloning largely positive?

8) What problems would also apply to cloned animals?

9) How long ago did the research on cloning begin?

10) What is one of the main puzzles in developmental biology?

 

Systems of breeding

1. Read and translate the texts:

Cross-breeding.

Cross-breeding is the system of mating animals of different breeds. To be successful it must be planned and the parents must be carefully chosen. When there is no planning or control, the results are usually unsuccessful. Good cross-breeding can give very good results and is used widely in the breeding of nearly every class of stock.

There are two main reasons for cross-breeding. The first is to combine the desirable characteristics of two or more breeds and the second is to get some degree of heterosis or hybrid vigour.

No breed is perfect in every way. Some are well-known for one character, some for another. If good characters of one breed can be combined with the good characters of another breed, it may be possible to produce an animal which is better suited than its parents to a particular market or particular condi­tions.

The offspring from cross-breeding are usually referred to as half-breeds or crosses.

The sheep industry in Great Britain is one of the best examples of planned and efficient cross-breeding. The moun­tain breeds such as Scotch Blackface, Swalesdale, Cheviot and Welsh Mountain are very hardy and very good mothers but they are rather small, not very prolific and their lambs are not suitable for the fat lamb production. Therefore they are crossed with a long-wool ram such as the Border Leicester, Hexham Leicester, Wensleyday or Teeswater that are noted for size and prolificacy.

Cross-breeding can produce new breeds. This type of breed­ing is usually carried out by research stations. It takes many years to produce a new breed. Recent examples are the Colbred breed of sheep. The devel­opment of this breed has taken ten years.

Breeds are also interchanged between countries. The Lin­coln Long-wool was imported from Britain to Australia and crossed with the Merino breed. This combination has resulted in a new breed, the Corriedale which is better suited to Austra­lian conditions and wool production.

Heterosis is the second important reason for cross-breed­ing. The term is used to explain the fact that hybrids or cross­breeds are usually better or more vigorous than their parents.

For example, a recent analysis of 34,000 recorded litters off pigs showed that mating pure-bred sows to a boar of a different breed resulted in 2 per cent more pigs at birth, 5 per cent more pigs at weaning, 10 per cent greater litter weight at weaning compared with pure-bred sows mated to boars of the same breed. Cross-bred sows gave even better results. In other words, there were more pigs born, more of them survived and they grew and thrived better than the pure-breeds. The characters of prolificacy, hardiness and early growth rate are the nods characters included in the term "hybrid vigour".

Mating of Animals of the Same Breed.

There are many breeds in all classes of stock, some being more popular than others. The more popular breeds usually possess one or more valuable characteristics in some high degree. Developing that character within the breed will greatly improve it.

There are two main possibilities to improve the stock by mating them to animals of the same breed. They are using animals that are known to be related or animals that are eith­er not related or very distantly related.

Outcrossing.

Outcrossing is the term used in practice of mating stock that are unrelated.

The main object of outcrossing is to bring into the herd some desirable character which the herd lacks. For example, if a herd is low in butterfat, the surest method of improvement would be to use a bull which comes from a line noted for high butterfat, unless it is the management or feeding that is at fault. Cross-breeding can be used too but it will almost cer­tainly add some characters that are not good.

Another reason for outcrossing is to restore some of the vigour that often found lacking where prolonged close-breeding has been practiced.

Inbreeding.

Inbreeding is the practice of mating very closely related animals. The use of inbreeding will result in the appearance of some poor animals, and the closer the mating the sooner they will appear. Hence, the inbreeding has to be accomplished by severe culling of the poorer stock to be effective as a breeding system. This is too expensive and few breeders can afford to improve their stock in this way. This method is widely used in poultry at present. Its possibilities are being increasingly explored in other classes of stock.

Line-Breeding.

 Line-breeding is the practice of close-breeding where the animals are not closely related. In practice, line-breeding is the breeding back to a certain excellent sire or dam or to a family with which that sire or dam was associated. Good characters are preserved in this way and at the same time the relationship is not close enough to produce any of the ill effects of inbreeding.

Artificial insemination technique is known to be a valua­ble aid in carrying out various mating systems. As in this case semen can be frozen, transferred and kept for long pe­riods to be used at any time in the future.

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