I found difficulty in understanding the problem of telomers replication.
In particular, every molecular biology book explains that there is a problem with replication of 3′ of the template DNA for the lagging strand because the very extremity is occupied by the first RNA primer and so we need telomerase to extend the template.
But why shouldn’t we consider the same problem with the 3′ extremity of the template for leading strand DNA? We need to hybridize it with a RNA primer, too, and if we don’t replace it with some DNA some nucelotides will be lost in the "son" strand.
I did not do a biology book review. But I always considered that the question of replication of telomers is similar for the leading strand and the lagging strand. In the absence of telomerase activity I guess that both strands shorten at each DNA replication.
Telomeres are short repetitive sequences of DNA that cap the ends of chromosomes. Due to the end replication problem that the lagging strand of DNA is unable to copy the very tip of the chromosome, as well as susceptibility to oxidative stress, telomeres shorten with every cell division https://en.wikipedia.org/wiki/Telomere
Telomeres have been compared with the plastic tips on shoelaces because they keep chromosome ends from fraying and sticking to each other, which would destroy or scramble an organism’s genetic information. Yet, each time a cell divides, the telomeres get shorter. When they get too short, the cell can no longer divide; it becomes inactive or "senescent" or it dies. This shortening process is associated with aging, cancer, and a higher risk of death. So telomeres also have been compared with a bomb fuse. https://www.boundless.com/biology/textb … 438-11663/