DNA Replication & Repair MCAT Practice Question
During mismatch repair in E. coli, the MutS protein recognizes distortions in the DNA helix caused by base mismatches. The repair machinery must distinguish the newly synthesized strand from the template strand to remove the incorrect nucleotide from the correct strand. What modification on the newly synthesized strand guides the mismatch repair machinery to target the correct strand for excision?
Answer choices
- APhosphorylation of thymine residues
- BPresence of 3' overhangs
- CIncorporation of uracil instead of thymine
- DLack of methylation at GATC sequencesCorrect answer
- EIncreased density of histone proteins
- FPresence of nicks in the sugar-phosphate backbone
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