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:

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: