For General Science, MBBS, BDS, MD students

1. MUTATION
Prof (Dr) Viyatprajna Acharya, MBBS, MD, PhD

2. Permanent changes in DNA sequence
• Germ cell mutation – Inherited
diseases
• Somatic cell mutation– Cancer or
malfunctions

3. Are they all harmful???
• Diseases- inherited diseases, cancers,
malfunctions
• Helps is survival- Apolipoprotein AI
Milano (AIM), LRP-5 (Low density
lipoprotein receptor related protein),
malaria resistance in African tribe
having HbC

4. What leads to mutation?- Mutagens

5. How fast it takes place???
• Every generation DNA is passed- 100-200 new
mutations
• One mutation in every 30 million bp
• Initially the changes do not appear in
template strand– later moves to template
strand in daughter DNA

6. Types of mutation
Base substitution or Point mutation
(Transition or Transversion type)
Frame shift mutation
Silent Mis-sense Nonsense Deletion Insertion
Acceptable Partially acceptable Unacceptable

7. Transitions Vs Transversions
• Transition- Purine for Purine or Pyrimidine for
Pyrimidine
• Transversion- Purine for Pyrimidine and the
vice versa

8. Point mutation
• Only one base is altered
• Protein with abnormal AA sequence
• May be of 2 types:
Transition– Purine replaced by purine or
Pyrimidine replaced by Pyrimidine
Transversion – Purine replaced by
Pyrimidine or vice-versa

9. Effect of Point mutation
• Silent mutation– no change in AA sequence;
Degeneracy responsible
• Mis-sense mutation – Different AA sequence
; can be acceptable, partially acceptable or
unacceptable
• Nonsense mutation– A stop codon is inserted;
non-functional protein e.g. Thalassaemia

10. Mis-sense mutation
1. Acceptable– Hb-Hikari ; Asp replaces Lys
at 61st position of β-chain- normal
function unaltered
2. Partially acceptable – HbS (Sickle cell
disease) ; β6 Glu → Val
3. Unacceptable – HbM (Methaemoglobin);
α 58 His → Tyr; Non-functional Hb

11. Frame shift mutation
• Insertion or deletion of one or two
nucleotides in DNA
• Whole reading frame alters
• Deletion frame shift mutation– Cystic fibrosis
of pancreas
• Insertion frame shift mutation --
Thalassaemia

12. Suppressor t-RNAs
• Doing the right thing-- by a wrong t-RNA
• They are malfunctional
• Bind to altered codons
• Can be a tool for inserting desirable codons at
specific sites

13. When GOD solves your problems, you have
faith in HIS abilities; when GOD doesn't solve
your problems HE has faith in your abilities.

14. www.vpacharya.com