Subject: Activation energy for DNA replication

Since I have not studied biology, I have been going through my daughter's high 
school biology book to get a basic understanding of the subject. I have a 
degree in engineering and I find this area very fascinating. In reading about 
DNA replication, it occurred to me that the process would be associated with 
an activation energy as the hydrogen bonds first break up during the parent 
DNA unzipping process and then recombine with the new sugar-phosphate daughter 
strands. Is this correct? If so, how is this energy supplied and what is its 
magnitude? On a more fundamental level, I assume the original hydrogen bonds 
in the parent DNA must attain a level of instability to trigger the bonds to 
break to start the unzipping process; otherwise, why would the nitrogen bases 
want to recombine to form a new set of DNA strands if it is already in a 
stable state? If this is correct, what mechanism triggers this instability and 
does it occur in some periodic manner? I would appreciate a simple answer.

Re: Activation energy for DNA replication