telomerase

According to a research done by a team of researchers at the University of Texas, An evaluation of cell lines from 18 different human tissues revealed the presence of telomerase in 98 of the 100 immortal cell lines, telomerase was not found in any of the 22 mortal cell lines.Telomeres is a repeated DNA sequence(TTAGGG) found at the ends of linear chromosomes that protect the ends of the chromosome from degradation, or telomere can be defined as DNA sequences found at the ends of eukaryotic chromosomes which maintain the fidelity of genetic information during replication. At birth as determined by terminal restriction fragment analysis, telomeres consist of about 15,000 base pairs of repeated TTAGGG DNA sequences, which become shorter with each cell division owing to the end replication problem. Every time a cell divides it loses 25-200 DNA base pairs off the chromosomes. It is possible that mortality stage 1 may be induced by the activation of genes located in the immediately subtelomeric region of the chromosomes.The second is the mortality stage 2 which represent the physiological result of critically short telomeres when cells are no longer able to protect the ends of the chromosomes, so that the end degradation and end to end fusion occurs and causes genomic instability and cell death). While researching on a topic like this, couple of important questions came to mind, so I made effort to research and address some of these questions which might be considered important. One of such questions is why do telomeres shorten? the mechanism of DNA replication is different in linear chromosomes is different for each of the two strands, known as leading and lagging strands. the lagging strand is made as series of discrete fragment, each one requiring a new RNA primer to initiate synthesis. the DNA between the last RNA priming event and end of the chromosome cannot be filled in.{this process is known as the end replication problem} since a strand cannot copy its end,