Mutagens: How the Environment Affects Mutation Rates

The environment we live in has a real impact on whether we experience genetic mutations. The quality of water we drink and the air we breathe can actually affect the integrity of our DNA. Our bodies are designed to correct any mistakes, but dangers from the environment can increase our chances of ending up with a mutation. An environmental agent that causes a mutation is called a mutagen.

There are over 70,000 man made chemicals available commercially, including

fertilizers, preservatives, pesticides, herbicides, drugs, etc. that we may ingest.

Many natural compounds that may occur in our air, food and water are also

potential mutagens.

Ever since the time of H.J. Muller(1927) who reported that X-ray could induce mutations in Drosophila a large number of agents or factors have become available to induce mutations.

Many natural compounds that may occur in our air, food and water are also potential mutagens.

Ever since the time of H.J. Muller(1927) who reported that X-ray could induce mutations in Drosophila a large number of agents or factors have become available to induce mutations.

Mutagenesis is the process of producing a mutation. If it occurs in nature without the addition of a known mutagen, it is called spontaneous mutagenesis and the resulting mutations are spontaneous mutations.

A mutant refers to an organism in which either the base sequence of DNA or the phenotype has been changed.

Mutagens are of three types: physical, chemical and biological.

Physical mutation of DNA can be caused by ionizing radiation, ultraviolet radiation and by mineral fibres. These three mutagens act in very different ways.

1. Ionizing radiation literally punches holes in the DNA, breaking the correct genetic sequence. Ionizing radiation can come directly from X-rays and solar radiation (cosmic rays) and indirectly from radon gas.

2. Ultraviolet radiation, which comes from the sun, induces mutations by causing certain portions of DNA to remain bound together (even when they shouldn’t).

3. Certain natural mineral fibres like asbestos, because of their size, can cause damage directly to DNA resulting in carcinogenic mutations.

In the case of chemical mutagens, mutation is caused by foreign molecules binding to a cell’s DNA, causing it to be ‘misread’. Examples of chemical mutagens are benzopyrene (found in cigarette smoke), vinyl chloride (found in the plastics industry), aflatoxin (found in certain moulds) and hetrocyclic amines (found in over-cooked foods).

Biological mutagens

Biological mutagens may be viral or bacterial. Viral mutagens may use a number of different complex mechanisms to cause a cell to become cancerous. Viruses that can be a risk factor for different cancers include the human papilloma virus (implicated in cervical cancer), the human T-cell lymphocytic virus (implicated in lymphoma), and the hepatitis B virus (implicated in liver cancer). One known bacterial mutagen is helicobacter pylori (implicated in stomach cancer).

IV. Answer the following questions to check how carefully you have read the text:

1. Does the environment we live cause genetic mutations?

2. What can dangers from the environment increase?

3. What is called a mutagen?

4. What are man-made chemicals that we may ingest?

5. Who reported that X-ray could induce mutations in Drosophila? When?

6. What is mutagenesis?

7. What is spontaneous mutagenesis?

8. What is a mutant?

9. What are the types of mutagens?

10. How can physical mutations of DNA be caused?

11. In what way does ionizing radiation affect DNA?

12. How does ultraviolet radiation induce mutations?

13. What is the harmful effect of certain mineral fibres?

14. What are the examples of chemical mutagens?

15. What viral mutagens do you know?

16. What does helicobacter pylori induce?

Дата добавления: 2015-10-26