Final answer:
DNA polymerase I is not suitable for long track DNA synthesis due to its lack of processivity and absence of a sliding clamp, which are crucial for continuous DNA synthesis. It mainly functions to replace RNA primers with DNA on the lagging strand during replication.
Step-by-step explanation:
The reason why DNA polymerase I is not suitable for long track DNA synthesis is not precisely listed in the options provided. However, based on our understanding of DNA replication, DNA polymerase I primarily functions to replace RNA primers with DNA and does not have the processivity of DNA polymerase III, which is the enzyme primarily responsible for synthesizing the new strand of DNA on the leading and the lagging strands. DNA polymerase I lacks a strong processivity because it does not have a sliding clamp, such as the beta clamp that holds DNA polymerase III onto the DNA strand for efficient synthesis of long DNA molecules.
During DNA replication, DNA polymerase III takes over most of the synthesis after RNA primers are placed. It is DNA polymerase I that comes in afterward to remove these RNA primers using its 5' to 3' exonuclease activity and fills in the resulting gaps with DNA. The sliding clamp is essential for DNA polymerases to stay attached to the DNA template for effective and continuous replication, especially on the leading strand and for the creation of Okazaki fragments on the lagging strand.
Lastly, it is the DNA ligase that seals the nicks after DNA polymerase I has done its job of primer removal and gap filling, ensuring the sugar-phosphate backbone of the DNA molecule is stable.