Q.What is the difference between missense and nonsense mutation ?

A mutation is a sudden, heritable change in the genetic material, a term coined by Hugo de Vries (1901) from his work on the evening primrose. Mutations are classified along several axes at once: by origin (spontaneous, with no known cause, versus induced, by a known mutagen); by cell type (somatic, not inherited, versus germ-line, inherited); by effect on gene function (loss-of-function/null, hypomorphic, hypermorphic, or gain-of-function/ectopic); and, for point mutations specifically (changes to one base pair or a small number of adjacent base pairs), by molecular type -- a base substitution is a transition (purine-to-purine or pyrimidine-to-pyrimidine, e.g. A to G) or a transversion (purine-to-pyrimidine or vice versa, e.g. A to T), while an indel is an insertion or deletion of one or more nucleotides. Judged by their effect once translated, a substitution can be silent/synonymous (same amino acid), missense/non-synonymous (different amino acid), or nonsense (creates a premature stop codon, UAA/UAG/UGA); an indel whose length is not a multiple of three causes a frameshift, scrambling every downstream codon. Agents that raise the mutation rate are mutagens: physical mutagens include heat (breaks DNA hydrogen bonds) and radiation, split into high-energy ionising radiation (X-rays, gamma rays, al …