Dynamics of telomere in ageing

Abstract

Telomere are composed of G rich nucleotide (TTAGGG)n typically 20 kb in length, are the regions of repetitive DNA at the end of the chromosomes. As the eukaryotic cells divide, the protective ends of the linear chromosomes, the telomeres, gradually shorten with each cell division. When a critical telomere length is reached, the cells are signaled into senescence, an irreversible state of quiescence. Thus, telomere length has emerged as replicative clock within each population of cells. Since telomere are also non coding sequence of DNA, as that of introns, there might be specific sites as of 5’ splice site and 3’splice site, which might be the conserved regions in telomere and can possibility generate a signal for apoptosis after a certain time of cell division.
Since Telomere Length (TL) in the somatic cells determines the number of cell divisions, TL has been proposed as a marker for biological ageing and cancer. Under conditions of chronic oxidative stress, the rate of telomere shortening is increased. Since telomeres consist of the repetitive sequence TTAGGG, and have a high GC content, they are very vulnerable to base oxidation. Additionally, DNA strand breaks are less efficiently repaired at the telomeres when compared to the rest of our genome. This means that reactive oxygen species cause more damage to the telomeres and this damage is less well repaired. Genetics play an important role in determining TL, but environmental and lifestyle factors such as smoking, alcohol consumption, physical activity, body composition and coffee and tea consumption can affect oxidative stress levels, which may contribute significantly to accelerated telomere shortening. Since, buccal cells are under direct contact with smoke and various toxic chemical substances in people who are acutely habituated with taking tobacco and cigarettes. So in our work we have found the conserved region of the telomere and showed the prolonged effect of tobacco and cigarettes on these conserved regions of the telomere.