Question

1. Make a list of induced mutagens. How does one differentiate between something that is spontaneous vs induced (clue: rate); what are some environmental mutagens; for each what type of mutations would they cause? Can the environment be a cause of spontaneous mutation?

Answer 1

Mutagen is a physical or chemical agent that can change the genetic material usually dna of an organism an causes mutation. Induced mutagens are of 3 types:-

physical mutagens:-

-ionizing radiation such as x-ray ,gamma rays and alpha particle

-ultraviolet radiations with wavelength above 260nm

Chemical mutagens:- hydrogen peroxide, nitrous acid, polycyclic aromtic hydrocarbon, alkylating agent, nitrosamines mustard gas and vinyl chloride, base analogs.

Biological mutagens:- virus, bacteria and transposon

* Spontaneous mutations occur naturally due to error in natural biological processes while induced mutations are due to agents in environment that cause a change in dna structure.

* Spontaneous mutations rate varies , it occurs at the rate of 10^-10 and 10^-15 per generation. While the rate of mutation in induced mutation can be increased by various factors.

- The ionizing radiation like x-ray and gamma ray cause dna breakage.

- the uv rays produce pyrimidine dimers which cause error in replication.

- deaminating agents cause transition mutation by converting cytosine to uracil.

- alkylating agent cause dna cross linking and breakage by transfering methyl or ethyl group to bases.

- base analogs can substitute for dna bases during replication and cause transition mutation.

* The cause of spontaneous mutation are still unknown . They seem to happen spontaneously without any outside influence. Environment does not causes spontaneous mutations rather it causes induced mutations.