Final answer:
The absence of Okazaki fragments in PCR is due to the method's use of continuous synthesis from primers on both strands of the targeted DNA segment, unlike the discontinuous synthesis required on the lagging strand in cellular replication.
Step-by-step explanation:
Okazaki fragments are short stretches of DNA synthesized on the lagging strand during DNA replication in cells. These fragments are produced because the DNA polymerase can only synthesize DNA in the 5' to 3' direction, leading to discontinuous synthesis on the lagging strand. Each Okazaki fragment begins with an RNA primer, which is later replaced by DNA nucleotides before the fragments are joined together by DNA ligase.
In polymerase chain reaction (PCR), Okazaki fragments do not form because PCR amplification is designed to replicate short regions of DNA with the use of a pair of primers binding to the opposite strands at the target sequence. Since the DNA polymerase used in PCR can continuously synthesize the new strands in the 5' to 3' direction from each primer without interruption, there is no need for the short, discontinuous synthesis characteristic of lagging strand synthesis in cellular DNA replication.
Thus, the absence of Okazaki fragments in PCR is due to the continuous synthesis occurring from both primers on the template strands, and the fact that PCR targets relatively short segments of DNA, which eliminates the requirement for the complex process encountered in lagging strand synthesis of cellular DNA replication.