This document summarizes types of DNA damage, including endogenous damage caused by reactive oxygen species and exogenous damage from radiation and toxins. It describes two main types of DNA damage - endogenous from metabolic byproducts and exogenous from environmental factors like radiation, toxins, and pollutants. Specific causes of exogenous damage discussed include radiation, natural toxins, polycyclic aromatic hydrocarbons, aromatic amines, and alkylating agents. The document concludes that DNA damage can lead to mutations and discusses the role of DNA damage in aging and cancer development.

1. GURU NANAK INSTITUTE OF PHARMACEUTICAL SCIENCE AND
TECHNOLOGY
TOPIC :Causes and types of DNA damage
NAME OF THE STUDENT: PIYUSH KARAN
UNIVERSITY ROLL NUMBER: 31308421024
ACADEMIC SESSION : 2022- 2023
PAPER NAME: MOLECULAR BIOLOGY
PAPER CODE: CMC303
Maulana Abul Kalam Azad University of Technology

2. INTRODUCTION
B. Sc./ SEM 3/2022-23/ Molecular biology/ CMC303/Presentation_1
• DNA damage exists in all cellular organisms. While DNA damage is distinguished from
mutation, mutation can result from unrepaired DNA.
• While most DNA damage can be repaired, such repair systems are not 100% efficient.
Un-repaired DNA damage accumulates in non-replicating cells, such as neurons or
myocytes of adult mammals, and can cause aging.
• DNA damage is induced via a wide spectrum of agents, both natural and made-made.
In the context of disease, DNA damage presents a paradox.
• DNA damage is typically associated. Nucleobase modification can give rise to
mutations. When situated in the region of DNA that codes for an appropriate gene,
the mutation can give rise to cancer

3. B. Sc./ SEM 3/2022-23/ Molecular biology/ CMC303/presentation_1
DNA damage can be subdivided into two types:
(1) endogenous damage-
• caused by reactive oxygen species (ROS) that are derived from metabolic byproducts
• thermodynamic stability and base-pair energetics of the incoming dNTP and template
base,
• the geometric selection of a correctly shaped and sized dNTP in the polymerase’s
activities,
• removing an incorrectly inserted deoxynucleotide by a 3′-5′ deoxynucleotide exonuclease
(2) exogenous damage -
• caused by radiation (UV, X-ray, gamma), hydrolysis, plant toxins, and viruses.
• Depending on the amount of energy transferred to matter, radiations are classified as
either high LET (alpha rays) or low LET (beta and gamma)
• Cumulatively, IR can damage the DNA either directly, or by indirect means, such as by
radiolysis of the surrounding water to generate a cluster of highly reactive hydroxyl
radicals (•OH)
TYPES -

4. B. Sc./ SEM 3/2022-23/ Molecular biology/ CMC303/presentation_1
causes -
• Toxins -
Natural toxins constitute a class of genotoxic and carcinogenic compounds,
which are normally used by microorganisms or fungi in defense response
• Environmental stresses -
Environmental sources of stress such as extreme heat or cold, hypoxia, and
oxidative stress
• Polycyclic aromatic hydrocarbon (PAH) -
Polycyclic aromatic hydrocarbons are carbon compounds with two or more
aromatic rings and are generally known to be inert, nonpolar and widely
distributed carcinogens in the environment.
• Aromatic amines -
Aromatic amines are principally produced from cigarette smoke, fuel, coal,
industrial dyes, pesticides and everyday high temperature cooking
• Alkylating agents -
Exogenous alkylating agents are primarily produced from dietary components,
tobacco smoke, biomass burning, industrial processing and chemotherapeutic
agents

5. CONCLUSION
SUMMARY
B. Sc./ SEM 3/2022-23/ Molecular biology/ CMC303/Presentation_1
This review outlines the basic types of DNA damage caused by exogenous
and endogenous factors, analyses the possible consequences of each type
of damage and discusses the need for different types of DNA repair. The
mechanisms by which a minor damaging event to DNA may eventually
result in the introduction of heritable mutation/s are reviewed. The major
features of the role of DNA damage in ageing and carcinogenesis are
outlined and the role of iatrogenic DNA damage in human health and
disease

6. REFERENCE
B. Sc./ SEM 3/2022-23/ Molecular biology/ CMC303/Presentation_1
1.Lewin B. Genes VIII. Prentice-Hall, Inc., Upper Saddle River, NJ 07458, USA, 2003.
2.Harper JV, Anderson JA, O'Neill P. Radiation induced DNA DSBs: Contribution from stalled
replication forks? DNA Repair (Amst). 2010 Aug 5;9(8):907-13.
3. Deshmukh PS, Megha K, Banerjee BD, Ahmed RS, Chandna S, Abegaonkar MP, Tripathi AK.
Detection of Low Level Microwave Radiation Induced Deoxyribonucleic Acid Damage Vis-à-vis
Genotoxicity in Brain of Fischer Rats. Toxicol Int. 2013 Jan;20(1):19-24.