Final answer:
The sequence at which DNA replication begins is typically AT-rich, which allows for easier unwinding of the DNA helix due to the fewer hydrogen bonds in AT pairs compared to GC pairs.
Step-by-step explanation:
The characteristic of the sequence at which DNA replication begins is that it tends to be AT-rich. This is due to several advantages that an AT-rich region provides for the initiation of replication. For example, adenine-thymine (AT) base pairs are held together by only two hydrogen bonds, compared to the three hydrogen bonds in guanine-cytosine (GC) pairs. Thus, AT-rich regions require less energy to separate, facilitating the unwinding and opening of the DNA double helix, which is necessary for replication to commence. In prokaryotic organisms like E. coli, the origin of replication known as oriC is an AT-rich region, which allows proteins that initiate replication to easily bind and start the replication process.