This document discusses different types of genetic mutations. It defines mutations as changes in DNA sequences and describes two main types - spontaneous mutations that occur naturally and induced mutations caused by external mutagens. The document then describes several specific types of mutations: transition and transversion base substitutions, missense and nonsense point mutations, frameshift mutations, neutral mutations, and silent mutations. It explains the molecular mechanisms and consequences of each type.

1. Mutation and its types
By,
Meghashree. A. M.

2. Contents
 Introduction
 Types of Mutation
 Conclusion
 References

3. Mutation
 Genetic variation among individuals provides the raw
material for evolution.
 Two major processes are responsible for genetic
variation, mutation and recombination.
 Mutations [Latin mutare, to change] were initially
characterized as altered phenotypes or phenotypic
expressions.
 In 1910, Hugo de vries gave the name mutation
when experiment on Oenothera lamarckiana
which shows spontaneous heritable changes.

4.  Mutations occur in one of two ways.
(1) Spontaneous mutations arise occasionally in all cells
and develop in the absence of any added agent.
(2) Induced mutations, on the other hand, are the
result of exposure of the organism to some physical
or chemical agent called a mutagen.
 Mutation may occur in somatic cell or germ cell.

5. Mutation
Substitution Addition or deletion
Transition
Transversion
Missense Nonsense
Neutral
Silent
Frameshift

7. Transition mutation
 In a transition, a purine nucleotide is replaced with a
purine nucleotide, or a pyrimidine nucleotide is
replaced with a pyrimidine nucleotide.

8. Transversion mutation
 In transversion, a purine nucleotide is replaced with a
pyrimidine nucleotide or a pyrimidine nucleotide is
replaced with a purine nucleotide.

10. Missense mutation
 A transition mutation from AT to GC change the
codon which leads to change in the aminoacid.

11. Molecular basis of sickle-cell anemia. Consequences of
base substitution example-missense mutation
The resulting hemoglobin is defective and tends to polymerize at low oxygen
concentration.

12. Nonsense mutation
 A transversion mutation change the codon leads to
termination of protein synthesis.

13. Neutral mutation
 A neutral mutation is a mutation that occurs in an
amino acid codon but it has no impact.
 A change in a base pair results in an amino acid
change but the new amino acid has the same
chemical properties as old amino acid.

14. Silent mutation
 In silent mutation, change in codon occurs such that
the same amino acid is specified.

15. Frameshift mutation
 Frameshifts usually caused by the deletion or
addition of DNA segments resulting in an altered
codon reading frame.

19. Conclusion
 Any change of nucleotide sequences in one genome
can be considered as “mutation”.
 Mutations occur in one of two ways i.e. Spontaneous
and induced.
 Mutation may leads to loss of function or gain of
function.
 Types of mutation are transition, transversion,
missense, nonsense, neutral, silent and frame shift.

20. References
 Krebs. J. E., Goldstein. E. S., Kilpatric. S.T., Lewin’s essential Genes, III edition,
2013, John and Bartlett learning, Burlington. (pp 22-25)
 Robinson. T. R., Genetics for Dummies, II edition, 2010(pp189-201)
 https://www.google.co.in/search?rlz=1C1ASUM_enIN788IN788&tbm=isch&q=tr
ansition+mutation&chips=q:transition+mutation,g_2:base+substitution&sa=X&
ved=0ahUKEwjTm8WWg-
_cAhUQcCsKHcYDDSEQ4lYILCgD&biw=1366&bih=613&dpr=1#imgrc=_
 https://biologydictionary.net/point-mutation/
 https://www.ncbi.nim.nih.gov/books/NBK21578/
 http://bmg.fc.ul.pt/Disciplinas/FundBiolMolec/11aMutationRepair.pdf