dna replication's synchronous qualification

Question

      In DNA replication, due to the it's 5'to 3' direction and synchronous qualification, one of the strand(1) can be continuous the other strand(2) needs to DNA  ligase, okazaki fragment and more RNA polmeryse et cetera so it is discontinuous. But if DNA replication werent synchronous, after finishing the strand(1)  replicated, (when strand(1) is replicating from begining to the end,  Single-strand DNA-binding protein is binding to strand(2)  (to just my assumption.)) strand(2) would be start and it would need just a only one RNA polymrase like the strand(1) and it would be a continuous strand too so DNA replication could be more quick.(Because it would not need to connect lots of okazaki fragment by using Dna ligase for strand(2) ec cetera.)

       What is the logic is that? I'm asking the logic because as ı learn the human biology ı can see everything has a interesting locig but ı couldn't understand here the reason why organism uses this long way instead of the short version.

     Thank you in advance.

Answer 1

Prokaryotes, like bacteria, most commonly replicate by "theta-replication" which is not all that different than what you described. However, eukaryotes have many problems with replication and needed novel solutions. The 2 problems relevant here are (1) eukaryotic chromosomes are linear, not circular, and (2) there is typically more than one chromosome/cell. Because bacterial chromosomes are easily 1/10th (or less) the size of a typical eukaryotic chromosome, they can get away with having only one origin of replication (Ori). In this way, they replicate similar to how you described. In order to increase the speed of replication in giant, linear, eukaryotic chromosomes, there are hundreds of origin of replication sites. The leading strand does replicate faster, but it too can only go as far as the next replication bubble (or end of the chromosome -- whichever comes first). The lagging strand must "wait" for the replication bubble to open up enough for it to replicate further. So, yes, what you suggest would sound faster in principle, but in practice, it would actually take longer. Also, you mentioned RNA polymerases and I just want to make clear that they have nothing to do with replication; only DNA polymerases (of which eukaryotes have 3) are important for replication.