BIOB11H3 Lecture Notes - Lecture 10: Xeroderma Pigmentosum, Ionizing Radiation, Non-Homologous End Joining
Document Summary
In an e. coli parent strand is methylated on a" which allows it to recognize the daughter strand from the parent strand. The newly synthesized strand gets checked by mmr machinery before it becomes methylated. Mmr only repairs errors on the daughter strand: mmr in eukaryotes happen in different ways but methods to distinguish the new strand in not clear. Ionizing radiation (x-rays, gamma rays), some chemicals, chemotherapy drugs, free radicals etc. cause breaks in both strands of dna. This can lead to serious consequences but can be repaired quickly through many alternate pathways: the most used pathway is the nonhomologous end joining (nhej). The way this pathway works is: a ring-shaped heterodimeric protein ku detects dsb, ku recruits dna-pkcs (dna-dependent protein kinase, catalytic subunit, dsb ends are brought together and joined (dna ligase iv) Dna repair: clinical implications: mutations in 7 different genes involved in ner (xpa-xpg) result in serious consequences.
