Adjust the length of telomeres is crucial in the process of senescencji cell immortalization and tumorigenesis . It occurs mainly due to the activity of telomerase . Telomerase is a DNA polymerase -dependent RNA specific for telomeric sections , which plays a crucial catalytic subunit hTERT (reverse transcriptase ) necessary for enzyme activity. The function of telomere - telomerase has been demonstrated in most tumor cells , stem cells and lymphocytes during differentiation and activation. Telomere length has traditionally been performed by Southern blot analysis , and telomerase activity by PCR . In recent publications presented method based on the technique of flow cytometry , for the assessment of telomere length and level of hTERT expression on a single cell. They offer a simple and rapid assessment , particularly useful in large-scale clinical trials.