DNA repair
by:S.Solali
Prepare for your exams
Study with the several resources on Docsity
Earn points to download
Earn points by helping other students or get them with a premium plan
Guidelines and tips
Prepare for your exams
Study with the several resources on Docsity
Earn points to download
Earn points by helping other students or get them with a premium plan
Community
Ask the community
Ask the community for help and clear up your study doubts
University Rankings
Discover the best universities in your country according to Docsity users
Free resources
Our save-the-student-ebooks!
Download our free guides on studying techniques, anxiety management strategies, and thesis advice from Docsity tutors
DNA overview, examining various ways DNA is damaged and how body adapts and repair DNA.
Typology: Slides
2016/2017
1 / 61
This page cannot be seen from the preview
Don't miss anything!
Related documents
Partial preview of the text
Download DNA Repair Mechanisms: A Comprehensive Overview and more Slides Biology in PDF only on Docsity!
DNA repair
by:S.Solali
Types of DNA Damage (cont.)
- Oxidative damage: guanine oxidizes to 8-oxo-guanine, also cause SS and DS breaks, very important for organelles
- Replication errors: wrong nucleotide (or modified nt) inserted
- Double-strand breaks (DSB): induced by ionizing radiation, transposons, topoisomerases, homing endonucleases, mechanical stress on chromosomes, or a single-strand nick in a single-stranded region (e.g., during replication and transcription)
DNA Repair
- (^) DNA damage may arise: (i) spontaneously, (ii) environmental exposure to mutagens, or (iii) cellular metabolism.
- (^) DNA damage may be classified as: (I) strand breaks, (ii) base loss (AP site), (iii) base damages, (iv) adducts, (v) cross-links, (vi) sugar damages, (vii) DNA-protein cross links.
- (^) DNA damage, if not repaired, may affect replication and transcription, leading to mutation or cell death.
Methyl-directed mismatch repair
- (^) If any mismatch escapes the proof reading mechanisms it will cause distortion of the helix.
- (^) This can be detected and repaired but it is important that the repair enzyme can distinguish the new strand from the old.
- (^) This is possible in E. coli because there is an enzyme which methylates the A in a sequence GATC. This methylation does not occur immediately after synthesis and until it does the two strands are distinguishable.
Mismatch repair
- (^) MMR system is an excision/resynthesis system that can be divided into 4 phases:
- (^) (i) recognition of a mismatch by MutS proteins,
- (^) (ii) recruitment of repair enzymes
- (^) (iii) excision of the incorrect sequence,
- (^) (iv) resynthesis by DNA polymerase using the parental strand as a template.
Methyl Directed MisMatch repair in E. coli
Methylataion and Mismatch Repair
Excision RepairExcision Repair
- **Conserved throughout evolution, found in all prokaryotic and eukaryotic organisms
- Three step process:
- Error is recognized and enzymatically clipped out by a nuclease that cleaves the phosphodiester bonds (uvr gene products operate at this step)
- DNA Polymerase I fills in the gap by inserting the appropriate nucleotides
- DNA Ligase seals the gap**
Base excision Repair
- (^) For correction of specific Chemical
Damage in DNA
- (^) Uracil
- (^) Hypoxanthine
- (^) 3-m Adenine
- (^) Urea
- (^) Formamidopyrimidine
- (^) 5,6 Hydrated Thymine
Base excision repair.
- (^) Consist of DNA glycosylases and AP
endonuclease
- (^) The DNA glycosylases are specific
- (^) Uracil glycosylase
- (^) Hypoxanthine DNA glycosylase
- (^) Etc…