I.Quick check

1. What is a mutagen? Give one example.

2. Distinguish between the genotype and the phenotype of an organism.

3. If a diploid organism has two different alleles for the same gene, is it homozygous or heterozygous?

4. Is weight in humans an example of continuous variation or discontinuous variation?

II. Using a monolingual English dictionary define the following genetic terms:

allele; homozygous; heterozygous; dominant; recessive; polygenic.

III. Find Russian equivalents to the following word combinations:

№	English term	Russian equivalent
1.	inherited variation
2.	spontaneous mutations
3.	recessive form
4.	to be easy to distinguish
5.	subtle differences
6.	genetic make-up
7.	observable or measurable traits
8.	human height and weight
9.	differences grade into each other
10.	considerable environmental influence
11.	to arise partly
12.	multicellular organisms
13.	to induce mutations
14.	base sequence
15.	to result from
16.	to result in
17.	beneficial mutation
18.	natural selection
19.	to be of immense importance

IV. Fill in the gaps with the words and expressions from the text:

1. Mutations can either … spontaneously or … by agents called mutagens.

2. Mutations are usually thought of as … and they often are.

3. Occasionally, a mutation is …, changing the phenotype so that an organism has a better chance of … and ….

4. Genetic differences reflect… of an organism, that is, its genetic ….

5. Mutations that affect large sections of a gene and chromosome mutations are often ….

6. Although beneficial mutations are …, they are found to happen sooner or later if there is a large … in a population.

7. A mutation is … in the amount or the chemical structure of DNA.

8. The genotype determines the … of an organism, whereas the environmental factors to which it is exposed determine to ….

9. In continuous variations, differences are ….

10. In discontinuous variations, the differences are ….

V. Find English equivalents to the following word combinations:

№	Russian term	English equivalent
1.	возникать спонтанно
2.	уровень спонтанных мутаций варьирует
3.	оказывать негативное воздействие
4.	доза радиации
5.	члены одного вида
6.	влияние окружающей среды
7.	видимые или измеряемые характеристики
8.	взаимодействие генотипа и окружающей среды
9.	существующий набор генов
10.	быть результатом замещения
11.	поражать большие наборы генов
12.	нуклеотидная последовательность
13.	функционировать нужным образом
14.	незначительные различия

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