Mutation is a change in the genetic material of an organism brought by the agents called the mutagens. They can be classified into the following.
(1) Physical mutagens- They include the ionizing radiations like the gamma rays and the X rays and non-ionizing radiation like the ultraviolet rays (UV).
(2) Chemical mutagens- They include nitrous acid, ethidium bromide, base analogues like 5-bromo uracil.
(3) Biological mutagens- They include the transposons and the viruses.
The ionizing radiations like the gamma rays and the X rays carry energy to liberate electrons from molecules and cause direct damage to the DNA, whereas the non-ionizing radiation like UV cause pyrimidine dimers causing errors in replication leading to mutation.
Nitrous acid is a deaminating chemical mutagen causing transition mutation by converting cytosine to uracil. Intercalating agents like Ethidium bromide change the DNA by inserting themselves and base analogues like 5-bromo uracil are similar to the nitrogenous bases of the DNA and can be inserted during the replication of DNA.
Transposons or the jumping genes are the sections of DNA that can be translocated to a different part of the DNA causing change in the DNA sequence and viruses insert their genetic material into the host cells and cause mutation.
