Telomere replication:

Replication of a linear DNA molecule in a eukaryotic chromosome builds a problem that does not exist for the replication of bacterial circular DNA molecules. The general mechanism of DNA synthesis means in which the 3' end of the lagging strand is not replicated.  This establish a gap at the end of the chromosome   and thus   a shortening   of the double-stranded   replicated portion.  The  effect  is which  the  chromosomal  DNA  would  become  shorter  and shorter  following  each  replication.  Several mechanisms have included solving this problem. In several organisms the solution is to use an enzyme known telomerase to replicate the chromosome ends.

Every telomere contains several copies of a repeated hexanucleotide series which is G-rich in Tetrahymena that is GGGTTG. The Telomerase carries as an integral component of its structure an RNA   molecule element of that   is complementary   to this G-rich sequence. The exact mechanism of action of telomerase is not clear in the figure shows one possible model.  RNA molecule of telomerase is envisaged to hydrogen-bond to the telomere end. That using the RNA as a sample, telomerase copies the RNA template therefore this enzyme is a reverse transcriptase and adds six deoxynucleotides to the telomere DNA end. The Telomerase then dissociates from the DNA rebinds at the new telomere end and repeats the extension procedure. It can do this hundreds of times before lastly dissociating. The latest extended DNA strand can then act as a template for normal DNA replication lagging strand synthesis by DNA polymerase α to form double-stranded chromosomal DNA.  The two procedures,  of the DNA  ends  shortening  through normal  replication  and  of  lengthening  using  telomerase  are  extremely  roughly  in balance so which every chromosome stays approximately  the similar length.