exposure to uv light thymine dimer no replicating dna strand
TRANSCRIPT
GROUP 4
XERODERMA PIGMENTOSUM
INTRODUCTION
XERODERMA PIGMENTOSUM, OR XP,
IS AN AUTOSOMAL RECESSIVE GENETIC DISORDER OF DNA
REPAIR IN WHICH THE ABILITY
TO REPAIR DAMAGE CAUSED BY ULTRAVIOLET (UV) LIGHT
IS DEFICIENT.
NORMAL CONDITIONwithout XP
DNA DAMAGES
Exposure to UV light Thymine dimer
No replicating DNA strand
REPAIR SYSTEMNucleotide excision repair
Recognization
Unwinding
Cleavage
Filling
Sealing
ABNORMAL
skin
NUCLEOTIDE EXCISION REPAIR
• Uvr-ABC excinuclease
• DNA Polymerase• DNA Ligase
GENE
SKINThe POL H gene
(encoded DNA polymerase eta (Pol η))
protecting cells from UV
thatinduced DNA damage
fix DNA damage
UV
Xeroderma pigmentosum
Type A, I, XPA Type E, V, XPE
Type F, VI, XPFType B, II, XPB
Type G, VII, XPGType C, III, XPC
Type V, XPVType D, IV, XPD
Type of XP & inherited mutation gene
autosomal recessive genetic disorder of DNA repair
Signs and Symptoms ofXeroderma Pigmentosum
Severe sunburn when exposed to small amounts of sunlight. These often occur during a child's first exposure to sunlight.
Development of many freckles at an early age
Skin Cancer
Eyes that are painfully sensitive to the sun and may easily become irritated and bloodshot
Blistering on minimum sun exposure
Spidery blood vessels
Scaly and dry skin
Irregular dark spots on the skin
freckles
blister
Scaly skin
blister
Bloodshot
DIAGNOSIS Usually detected in early infancy 1-2 years Clue to diagnosis - severe sunburn after first
exposure to the sunlightThe diagnosis of XP is made on the basis of
clinical findings and family history The diagnosis of XP is based on skin, eye, and
nervous system XP can be diagnosed by measuring the DNA
repair factor from skin or blood sample
Treatment For XP
Protection from UV
Eye and skin exam
Prompt removal of cancerous
tissue
Neurological exam
Psychososial care
INCURABLE
PrOGNOsi$
*Many patients die at an early age from skin cancers.but,if a person is diagnosed early, does not have severe neurological symptoms and takes all the precautionary measures to avoid exposure to UV light, they may survive beyond middle age.
< 40% of individuals with the disease survive beyond age 20. Some with less severe cases manage to live well into their 40s
CONCLUSION
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