1. DNA Damage Caused by
Ultraviolet Radiation
By: Nicolle A. Rosa Mercado
By: Nicolle A. Rosa Mercado
By: Nicolle A. Rosa Mercado

2. Introduction
-DNA:
-Most important molecule for every
living organism
-Contains the instructions necessary
for every living organism to function
-Alterations in it may lead to genetic
disorders and cancer
-Ultraviolet (UV) radiation:
-Uncontrollable environmental factor
that alters DNA sequences
-Its damage may cause cells to restrain
RNA synthesis (Moné MJ et. al 2001)
Fig. 1: This image is an example
of a possible alteration in a DNA
sequence.
earthobservatory.nasa.gov

3. UV Radiation
-Type of electromagnetic radiation that has a
shorter wavelength than that of the visible light.
-Three types of UV radiation:
- UV-A (400nm-315nm): found in black lights
- UV-B (315nm-280nm): most dangerous type
- UV-C (280nm-200nm): germicidal
Fig. 2: This image is an
explanation of the light
spectrum
flightspectrumllc.com

4. How UV radiation may be beneficial
-May create resistance to certain
pathogens in plants
-Used as a treatment for people with
vitiligo for humans
-Used to purify drinking water due to its
germicidal properties
-Helpful in studies that involve
spectophotometry and molecular genetics.
Fig. 3: This image shows the hands
of a vitiligo patient. UV-B light is
used to restore the pigmentation
of their skin.
Fig. 4: This image shows the machinery
used to purify drinking water
with UV radiation

5. Cyclobutane pyrimidine dimers (CPDs)
and 6-4 photoproducts(6-4 PPs)
-Lesions in the DNA sequence caused by UV
exposure (De Lima-Bessa KM et. al. 2007)
-May be responsible for the formation of clusters that
might lead to skin carcinomas
-Promote apoptosis provoked by UV exposure in
cells that lack NER
-Can obstruct DNA transcription and replication
-Fixed through DNA repair mechanisms

6. DNA Repair Mechanisms
-Cannot always detect the mutations due to defects in the
repair mechanisms themselves
-Important for maintaining the DNA sequence stable.
-A type of DNA repair mechanism is nucleotide excision
repair (NER), which corrects different types of damages
including thymine dimers provoked by UV radiation.(
http://www.nature.com/scitable/topicpage/dna-damage-repair-mechanisms-for-maintaining-dna-344)

7. NER Flow Chart
Fig. 5: This image shows how NER works. It consists of four proteins UvrA, UvrB,
UvrC, and UvrD. UvrA and UvrB search for mutations in the sequence, UvrC makes
cuts in the region of mutations so UvrD can remove them from the sequence. DNA
polymerase and DNA ligase then restore the sequence to the way it was before the
mutation occurred.
http://highered.mcgraw-hill.com/sites/dl/free/0072835125/126997/animation33.html

8. UV radiation and cancer
-Three types of cancer caused by UV radiation:
-Basal Cell Carcinoma: innermost part of the
epidermis; not a big threat
-Squamous Cell Carcinoma: upper part of the
epidermis; not a big threat
-Melanoma: most dangerous type of skin cancer;
develops in skin cells known as the melanocytes

9. UV radiation and cancer
Fig.6: This image shows how
squamous cell carcinomas and
basal cell carcinomas look on the
outer part of the epidermis.
Fig. 7: This image demonstrates
how melanoma affects the
inner and outer epidermis and
the dermis.

10. -It is very important to understand this topic due to the fact that
UV radiation is an uncontrollable factor that can affect our health
in a great way.
-Understanding how UV radiation relates to DNA repair
mechanisms might help with the discovery of new techniques to
maintain stability in DNA sequences.
Importance of this study

11. Conclusion
-DNA is the most important molecule in every organism and it is highly
susceptible to UV radiation.
-Although DNA has highly specific repair mechanisms, some mutations
caused by UV can be ignored due to a defect in the repair mechanism.
-Ultra-violet radiation causes DNA damage such as CPDs and 6-4 PPs that
may lead to cancer.
-Melanoma is the most dangerous type of skin cancer.
-UV radiation presents a mayor threat to our health because of its ability
to damage DNA sequences.

12. References
-Bernard A. Kunz, Paige K. Dando, Desma M. Grice, Peter G. Mohr, Peer M. Schenk, and David M. Cahill,
(October 2008), UV-Induced DNA Damage Promotes Resistance to the Biotrophic Pathogen
Hyaloperonospora parasitica in Arabidopsis, Rockville, United States, American Society of Plant
Biologists,148:1021-1031
-de Lima-Bessa KM, Armelini MG, Chigancas V, Jacysin JF, Amarante-Mendes GP, Sarasin A, Menck CFM,
(December 2007), CPDs and 6-4PPs play different roles in UV-induced cell death in normal and NER-
deficient human cells, Brazil, DNA Repair, 7:303-312
-Hidawi. June 2010. India. September 2010. Available at:http://www.hindawi.com/journals/jna/2010/592980/
-Moné MJ, Volker M, Nikaido O, Mullenders LHF, van Zeeland AA, Vershure PJ, Manders EMM, van Driel
R, (September 2001), Local UV-induced DNA damage in cell nuclei results in local transcription inhibition,
Amsterdam, EMBO Reports, 21:1013-1017
-Nijhofa JGW, Muldera, Aat M, Speksnijderb, Ewoud N, Hoogervorstb, Esther M, Mullendersc, Leon HF,
De Gruijl, Frank R, (July 2007), Growth stimulation of UV-induced DNA damage retaining epidermal basal
cells gives rise to clusters of p53 overexpressing cells, The Netherlands, DNA Repair 6:1642-1650
-Oh K, Bustin M, Mazur S, Appellac E, Kraemer K, (September 2010), UV-induced histone H2AX
phosphorylation and DNA damage related proteins accumulate and persist in nucleotide excision repair-
deficient XP-B cells, United States, DNA Repair, 10:5-15.
-Scitable. 2008. Nature Education. 2008. Available at: http://www.nature.com/scitable/topicpage/dna-
damage-repair-mechanisms-for-maintaining-dna-344

13. Any Questions??