Question

Mutagens: Chemical mutagens: Nitrous acid: Nucleoside analogs: Benzopyrene: Aflatoxin: Acridine dyes: Radiation: X-rays and gamma rays: Ultraviolet rays:

Answer 1

Mutagens: Mutagens are the component or substance that cause mutation. Mutagens can be chemical or physical.

Chemical mutagens :

1. Nitrous acid- Nitrous acid is chemical mutagen that acts on adenine, guanine, and cytosine. It converts adenine into hypoxanthine, cytosine into uracil and guanine to xanthine.

2. Nucleoside analogs-

The base analogues are chemicals that are analogue to bases of DNA- purine and pyrimidines. Hence they can cause mutation. Bromouracil and aminopurine are an example of base analogues of DNA that replace the normal bases, during the process of replication.

3. Benzopyrene- Benzo(a)pyrene is a chemical mutagen that metabolized to diol epoxide that binds covalently to guanine bases which prevent the base-pairing with cytosine bases.

4. Aflatoxin- Aflatoxins is a chemical mutagen that is produced by Aspergillus flavus and Aspergillus parasiticus. It is grown in soil, decaying vegetation, hay, and grains and toxic to human.

5. Acridine dye - Benzacridines are chemical mutagen that that leads to primarily base-pair substitution.  

Radiation- There are 3 types of radiation that cause mutation

1. X-ray and Gamma rays-

The lethal dose of X-ray (350-500 rems) breaks the phosphodiester bonds between the DNA and cause the strand breakages which leads to mutation. Gamma radiation is ionizing radiation that causes point mutation in DNA.

2. Ultraviolet rays-

UV-radiation causes base deletion and breakage of the strand.  It also forms nucleotide dimers like thymine dimers.