Telomeres

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Introduction

The field of telomere biology has been an active area of research in recent time, especially so following the work by Hayflick and Olovnikov. Expanding on his, Elizabeth Blackburn and Joseph Gall noticed that the end of the chromosomes from Tetrahymena thermophila contained the six base sequence TTGGGG iterated many times (Blackburn and Gall, 1978). Over the decades, literature has arisen that has revealed many things regarding telomeres. However, as with the case with many scientific endeavours, as one question is answered, another would arise. As a result, research in telomere biology has become one which many are deciding to take on.

We know that proper replication of the telomeric DNA at chromosome ends is critical for
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The main purpose of eukaryotic telomeres is to protect the genetic information at the ends of chromosomes from being shortened during DNA replication. This protective function of the telomere aims to safeguard chromosome ends from DNA degradation, DNA repair mechanism and to prevent end-to-end fusion between separate chromosomal ends; all of which will result in chromosomal instability, cellular senescence and apoptosis (O 'Sullivan and Karlseder, 2010). Since DNA replication can only occur in the 5’ to 3’ direction and requires a primer, it is not possible for DNA polymerase to replicate the 3’ ends of linear chromosomes, and the ends of the chromosomes would not be replicated. Telomeres are subsequently shortened during the process of replication; this way the coding section of DNA is preserved. Because of this, there is a strong implication between short telomeres and many age-related diseases (Harley, Futcher and Greider, …show more content…
Telomerase, due to its TERT sub unit, is an enzyme that has a reverse transcriptase function (Autexier and Lue, 2006). The TTAGGG repeat sequences can be added to each telomere structure since it can use a short RNA strand as a template to synthesise telomeric DNA repeat sequences at the end of chromosomes, lengthening the telomeric sequence, this was true in Tetrahymena thermophila (Blackburn, 1991). From Hayflick’s observation in 1965, it is now known that each somatic cell division shortens telomeres by up to 100 base pairs, and since most somatic cells do not contain telomerase, those cells will die after a certain number of cell divisions (Harley, Futcher and Greider, 1990). Interestingly, cancer cells contain telomerase, and therefore, they have the ability to proliferate new telomeric DNA

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