Final answer:
The 3' LTR is completed by telomerase, which extends the DNA strand using its RNA template to maintain chromosome integrity during replication.
Step-by-step explanation:
The other, 3' LTR (U3-R-U5), is completed through the action of the telomerase enzyme, which extends the 3' end of the DNA strand to ensure that important genetic information is not lost during replication. Telomerase adds nucleotides to the overhang of the telomere, compensating for the shortening that occurs in standard DNA replication processes.
This extension allows for the RNA primer of the last Okazaki fragment to be placed and extended, eventually leading to the formation of a complete 3' LTR. Telomerase has its RNA template which is used to add DNA repeats to the end of chromosomes, thus maintaining their length and integrity.