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

Listen to the recording. Repeat each medical term during the pause in the recording. Mind the stress

assay	1) анализ; пробирный анализ; биологическое испытание, тест, проба; количественный анализ; производить анализ; испытывать; 2) проба; образец для анализа
dihydro -testosterone	дигидротестостерон
embryo	зародыш, эмбрион (на протяжении первых восьми недель внутриутробного развития)
embryogenesis	эмбриональное развитие, зародышевое развитие, эмбриогенез
estrogene	эстроген (1. женский половой гормон; 2. эстрогенное средство)
inhibiting	ингибирующий
luteinising hormone, LH	лютеинизирующий гормон, лютропин, пролан Б(устар.), ЛГ
polymerase	полимераза
SRY-gene	ген SRY
testosterone	тестостерон
trigger	триггер, спусковой крючок, запускающий элемент
tumor	опухоль
Shereshevsky-Turner's syndrome	синдром Шерешевского-Тернера

Without looking into the text listen to the recording.

Say what information you have gathered.
Listen to the text again.

Now, read the text silently, trying to grasp all the details of the contents.

Then, read it simultaneously with the speaker, trying to catch up with the tempo.

After that read the text aloud, trying to imitate the intonation.

In humans the development of masculine sex is predetermined by the presence of Y-chromosome. Provided there is a Y-chromosome present, the number of X-chromosomes is irrelevant. There is a special SRY-gene located in a Y-chromosome that begins functioning on the 6^th-7^th week of embryogenesis. SRY-gene is a trigger activating a number of genes located in other chromosomes providing for the programme of testosterone synthesis in the embryo. It is the fetal testosterone that controls the masculine-type development of the embryo determining (together with anti-Mullerian inhibiting peptide) the development of internal, and, indirectly (through 5-a dihydro-testosterone), external masculine sex organs. SRY-gene also determines a high estrogene content (with part of testosterone converted into estrogens), thus suppressing the feedback between the luteinising hormone and estrogens in the developing brain. Such is the mechanism of the development of a non-cyclic hypotha-lamo-hypophysial regulation type of sex function and of the masculine type of brain. In the absence of Y-chromosome (and SRY-gene), when the karyotype is 46, XX or 45, XO (Shereshevsky-Turner's¹ syndrome), the aforementioned events do not take place and the somatic and psychic type developed is feminine.

The information on sex chromatin is used for the verification of chromosomal sex and sex chromosomes aberrations and for the approximation of the proliferative activity of tumors. There are several modern methods used for the verification of genuine sex, one of them is immune-enzyme assay of "masculine" antigen encoded by SRY-gene. Polymerase chain reaction (PCR) may also be used for verification of genuine gender because it can detect any gene. PCR may also be used for revealing genetic defects.

Answer the questions.

1. The presence of what chromosome is responsible for the development of masculine sex?

2. Does it matter how many X-chromosomes are present, provided there is аY-chromosome?

3. How many Y-chromosomes are required for the development of an organism according to the masculine type?

4. On which week of embryogenesis does a SRY-gene located in a Y-chromosome begin to function?

5. What genes does a SRY-gene activate?

6. What does the fetal testosterone control?

7. What is high estrogene content determined by?

8. Under what conditions is the feminine somatic and psychic type developed?

9. What are the data on sex chromatin used for?

10.What are modern methods such as immune-enzyme assay and polymerase chain reaction (PCR) used for?

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