BIOLOGY 1A03 Lecture Notes - Lecture 11: Ribosome, Arginine, Ornithine

• School: McMaster University
• Department: Biology
• Course: BIOLOGY 1A03
• Professor: Xudong Zhu

Document Summary

Can proofread own work-checks the match b/w paired bases= correct base pairs are energetically more favourable. If enzyme fis a mismatch, pauses and removes the mismatched base that was just added. Dna pol iii can do this b/c its (epsilon) subunit acts as exonuclease that removes deoxyribonucleotides from dna in 3" 5" direction (only if not h bonded to complementary bonded to base on strand) As a result, dna polymerase inserts the incorrect base only about every 100,000 bases added. Mismatch repair occurs when mismatched bases are corrected after dna synthesis is complete- ] removes incorrect base and fills in correct bases- 5 ! therefore the dna pol recognizes the lack of h bond and removes the c and replaces it with t. Mutations in genes encoding proteins responsible for mismatch repair dramatically increase mutation rates and some of them can give rise to hereditary non-polyposis colorectal cancer and variety of sporatic cancers.