2. Переведите следующие предложения на русский язык, используя лексику урока:

1. The term mass or phenotypic selection is the simplest form of selection. 2. The accuracy of genetic make up will result in degree of success attained. 3. Heredity partly determines such characters like egg-production in fowls or milk-production in cattle. 4. What evidence is there that animals’ good qualities are regularly transmitted from generation to generation? 5. If we have a good individual it will transmit its good qualities. 6. The average influence of any single animal in even the third of fourth ancestral generation is very slight.

3. Составьте аннотацию текста “Mass and Pedigree Selection”.

Text 9. Fixing Type

When there has been obtained an animal with something approaching the desired set of hereditary characters, the problem arises of maintaining of fixing this combination in a herd or flock or strain. It is true that no breeder has yet succeeded in producing a perfect animal, or even one possessing a full complement of all the best characters of its breed; yet success in the breeding of really fine individuals is comparatively common. It is far more difficult to build up a herd in which the good qualities are transmitted in any complete or regular fashion. For example, the milk production of cows. Individual yields of 2000 and 3000 gals., and even more, have been obtained. The best herds, on the other hand, produce averages of between 800 and 1200, and this under a system of continuous culling – that is to say, the average is not that of the females bred but the average after a considerable proportion of the poorest producers has been discarded. In many herds the average production is 400 gals. or less. Admitting that milk production is influenced by many circumstances other than heredity, one cannot avoid the conclusion that it is extremely difficult to get a fixed and true-breeding strain of heavy producers. It is obvious, too, that this end is of far greater importance than that of securing a few high individual records.

Лексические упражнения.

1. Выучите значение опорных слов:

to approach – приближаться; desired set of hereditary characters – желаемый набор наследственных черт; to fix – закреплять; flock – стадо; strain – порода; continuous culling – постоянная выбраковка; regular fashion – обычный окрас; circumstance – обстоятельство; heavy producer – животное с большой производительностью; heredity – наследственность; secure – укреплять, закреплять.

2. Образуйте существительные от следующих глаголов:

to classify, to employ, to decide, to expect, to consult, to possess, to expand, to provide.

3. Определите, к какой части речи относятся следующие слова:

simplest, hereditary, breeder, complement, comparatively, fashion, proportion, conclusion.

4. Заполните пропуски соответствующими предлогами.

1. It is true that no breeder has yet succeeded … producing a perfect animal.

2. The best herds, … the other hand, produce averages of … 800 and 1200 gals.

3. … many herds the average production is 400 gals or less.

5. Ответьте на следующие вопросы:

1. Why has no breeder succeeded in producing a perfect animal yet?

2. What kind of a herd is it rather difficult to build up?

3. What is milk-production influenced by?

4. Why is it extremely difficult to get a fixed and true-breeding strain of heavy producers?

Грамматические упражнения.

1. Переведите следующие предложения, обращая внимание на перевод безличных предложений:

1. It is true that no breeder has yet succeeded in producing a perfect animal.

2. It is far more difficult to build up a herd in which the good qualities are transmitted in any complete or regular fashion.

2. Образуйте 3 формы от следующих глаголов:

to arise, to build, to discard, to get, to influence, to obtain.

Упражнения для закрепления пройденного материала.

1. Переведите следующие предложения на английский язык, используя лексику урока:

1. Намного труднее организовать такое стадо, в котором нужные качества будут наследоваться из поколения в поколение. 2. На производство молока действует много факторов. 3. Важно сохранить средние показатели производства молока во всем стаде. 4. Самые продуктивные стада производят, в среднем, 800 – 1200 галлонов (3600 – 5400 литров) молока на корову.

2. Переведите следующие предложения на русский язык, используя лексику урока:

1. No breeder has yet succeeded in producing a perfect animal. 2. Individual yields of 2000 and 3000 gals, and even more, have been obtained. 3. Admitting that milk-production is influenced by many circumstances other than heredity, one should say to get a fixed and true-breeding strain of heavy producers it is extremely difficult.

3. Составьте аннотацию текста “Fixing Type”.

Text 10. Inbreeding

Inbreeding – the mating together of closely related animals – is a valuable aid in the fixing of type, i.e. in the production of strains in which the same characteristics are regularly reproduced.

In order to isolate “pure lines” from an ordinary mixed stock we should have to breed very closely for a considerable number of generations. In some cases it might take some twenty generations. Nothing approaching this amount of inbreeding has ever been attempted in practice, and so far we can only speak of strains of farm animals as relatively pure. Even in the most carefully selected and most closely bred families there must remain a considerable number of variable characters. That this should be so, in spite of the obvious advantages of pure-breeding types, is accounted for by another phenomenon connected with inbreeding.

Very generally, when attempts have been made to inbreed through several generations, the breeder has found that his stock deteriorated in some respect – showed a lack of size, or vigour, or both; susceptibility to disease; lessened fertility, or perhaps complete sterility. When we mate two animals, belonging to different inbred strains, the cross-bred progeny often show markedly greater vigour than either parent. This phenomenon is called “hybrid vigour” or heterosis.

Inbreeding does not lead to the creation of undesirable hereditary factors, but merely brings to light such as have been hidden. If the advantages of inbreeding, in the way of creating true-breeding types, are to be secured without the disadvantages of loss of vigour, etc., inbreeding must be accompanied by rigorous selection, so that, in practice, the degree of inbreeding that should be attempted must depend on the scope for selection. This, in turn, depends on the reproductive rate of the particular animal with which the breeder is concerned: for instance, there is far more scope for selection in poultry than in dairy cattle.

What is called “line-breeding” is merely a less intensive form of inbreeding. The term is ordinarily applied in cases where the degree of kindship, between animals mated, is less close. The most extensive experiments on the inbreeding of farm stock has been carried out with pigs.