Mutation is defined as the sudden heritable change in the nucleotide sequence of DNA in an organism. It is a process by which genetic variations are created which in turn brings about changes in the organism. The organism which undergoes mutation is called a mutant.

The factors which induce mutations are known as mutagens or mutagenic agents. 

Mutagens are of two types namely physical mutagens and chemical mutagens.

(i) Physical mutagens : Radiations like X-rays, a, (3 and yrays, UV rays, temperature etc. which induce mutations are called physical mutagens.

(ii) Chemical mutagens : Chemical substances that induce mutations are called chemical mutagens. 

Eg: Mustard gas and nitrous acid. The utilisation of induced mutation in crop improvement is called mutation breeding.

Achievements of mutation breeding: Some achievements of mutation breeding are-

(a) Sharbati Sonora wheat produced from Sonora-64 by using gamma rays. 

(b) Atomita 2 rice with saline tolerance and pest resistance 

(c) Groundnuts with thick shells