1. The origin of E. coli, oriC, is 245 base pairs and contains two elements that
ID: 195356 • Letter: 1
Question
1. The origin of E. coli, oriC, is 245 base pairs and contains two elements that play a significant role in the initiation of replication a) methylated GATC/CTAG repeats and b) 9 and 13 mer base repeats. Select one of these elements and explain their role/significance in the initiation of replication. (4pts) 2. Since SS8 does not have an enzymatic function, why is it essential for replication? (3 pts) 3. How does repair DNA synthesis differ from replication DNA synthesis? (3 pts) 4. Why would a DNA polymerase enzyme need to have nuclease activity? (3 pts)Explanation / Answer
Answer for question number 1 : Methylated GATC sequences in the OriC site helps the DNA repair machinery to descriminate between the parent and daughter strands. In this sequence Adenine is methylated by an enzyme called dam (Deoxyadenine methylase) which methylates adenine residues only in the parent strand/template strand. This helps the DNA repair machinery to descriminate between the template and the daughter strands which results in the repair of mismatches only in the daughter strand which is not methylated restoring the correct complimentary base pairs in the newly synthesised DNA strands.
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