Final answer:
Full-length DNA Pol I facilitates in vitro DNA synthesis via nick translation, extending the 3' end and removing the preceding strand with its 5'-3' exonuclease activity. This makes it useful not only in DNA repair and replication but also in experimental applications like DNA labeling for Southern blots.
Step-by-step explanation:
Full-length DNA Pol I is used for in vitro synthesis of DNA by nick translation. The process of nick translation involves the enzyme initiating DNA synthesis at nicks, or breaks, in the DNA. DNA Pol I extends the 3' OH end of the nicked DNA while concurrently removing the 5' strand ahead of the synthesis through its 5'-3' exonuclease activity. This activity is essential for displacing the existing DNA strand and replacing it with newly synthesized one. This unique property of DNA Pol I is important for DNA repair and DNA replication, specifically in the removal of RNA primers from Okazaki fragments and their subsequent replacement with DNA nucleotides on the lagging strand. Once the RNA primers are removed, the enzyme DNA ligase comes into play, sealing up the nicks left behind to form a continuous DNA strand.
In addition to its role in replication and repair, DNA Pol I's capacity to replace RNA with DNA while simultaneously degrading the RNA strand makes it a valuable tool for experimental procedures such as randomly labeling DNA probes for use in Southern blots, where DNA fragments are transferred to a membrane and then probed with labeled DNA sequences to detect the presence of specific DNA sequences.