Question

4. In E coli ,DNA replication is initiated when DnaA proteins bind to five DnaA boxes at the origin of replication and cause?
a. the AT-rich region to unwind
b.DNA polymerase to initiate
c. primase initiate synthesis of RNA
d. DNA to relieve supercoils
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Answer 1

Answer:

The correct answer is option a.

Explanation:

1. The E.coli has circular DNA.
2. Initiation of the replication requires two important regions of the DNA of E.coli.
3. One region contains 9 bp of 4 regions that acts as a recognition region.
4. The other region is 13bp long 3 regions upstream to the recognition region, and act as the origin of replication.
5. The enzyme DNAa binds to the recognition region and create stress and negative supercoil.
6. DNAb binds to the origin of replication and provide energy (ATP hydrolase).
7. The origin is rich in AT base pairs, having two hydrogen bonds between them.
8. The stress, negative supercoil and  ATP hydrolase cause the AT region to unwind.