After that read the text aloud, trying to imitate the intonation. Hereditary diseases are ailments caused by inherent defects in the genetic apparatus of the cell that are transmitted hereditarily through gametes

Hereditary diseases are ailments caused by inherent defects in the genetic apparatus of the cell that are transmitted hereditarily through gametes. Monogenous hereditary diseases are controlled by one gene and are subject to Mendelian laws (distribution), i.e. hemophilia A. Polygenous hereditary diseases are controlled by a summary effect of several differently located genes and are inherited according to the additive-polygenous principle, most likely with a threshold effect of the limiting factor. Although mutations are the basis of hereditary pathology, they are not identical to the hereditary diseases. Like all other ailments, hereditary diseases are caused by certain factors effective in particular conditions against the background of the reactivity of the organism. The effect of gene mutations may be compensated or altered either by the action of other genes, or by the environment, or by defensive mechanisms: counter mutation at the cellular, or other factors at the organism level, etc. There are no diseases determined exclusively by mutation. On the other hand, there are no diseases whose cause, development and effects are completely unaffected by heredity. Heredity is the basis for the reactivity of the organism. The effect of age and sex on the reactivity can be seen as the result of unfolding of the genetic programme.

3Answer the questions.

1. How can hereditary diseases be characterized in the most general terms?

2. Are monogenous hereditary diseases controlled by individual genes?

3. How many genes control polygenous hereditary diseases?

4. What distribution are monogenoushereditary diseases subject to?

5. What are polygenous hereditary diseases controlled by?

6. What constitutes the basis of hereditary pathology?

7 What factors cause hereditary diseases?

8. By what may the effect of gene mutations be compensated?

9. Are there any diseases determined exclusively by mutation?

10. Are there any diseases completely unaffected by heredity?

11. How are the notions of heredity and reactivity correlated?

4 Work in pairs. Ask and answer the questions above but not in the order they are listed in exercise 3.

5 Complete these words and word combinations below. (All the words may be found in the text above.)

1. r _ _ _ _ _ _ _ _ _ y

2. e _ _ _ _ _ _ _ _ _ t

3. c _ _ _ _ _ _ _ r

4. h _ _ _ _ _ _ _ _ a

5. M_ _ _ _ _ _ _ n d _ _ _ _ _ _ _ _ _ _ n

6. g_ _ _ _ _ s