Another cause of aging, on the molecular level, is telomeres. Telomeres are sequences on the end of DNA sequences that causes the DNA sequence to reduce over time. The shortening occurs on the lagging strand in DNA replication where the template stand is 5' to 3'. DNA can only be synthesized from 5' to 3'. Since DNA is antiparallel, meaning that one stand is going in the 3' to 5' direction and the other is going in the 5' to 3' direction. On the lagging stand, DNA would need to be synthesize in the 3' to 5' direction because the template is in the 5' to 3' direction. To fix this problem, Okazaki fragments allow the DNA to be synthesized in the 5' to 3' direction on the lagging strand. However, the DNA polymerase can not go to the end the lagging strand because there are not enough nucleotides to add an Okazaki fragments. In effect, telomerase (enzyme) extends the lagging strand to allow for more nucleotides to be added to the template strand so that the DNA will not be shortened. However, telomerase adds non-coding repeating sequences to the DNA that does not contribute to the functionality of the DNA. Telomeres have been associated with aging and cancer through studies. The more shortening of DNA is inhibited the less likely that any type of diseases will occur.