AP BIOLOGY

Detailed explanation-1: -Because telomerase is expressed in germ line cells and cancer cell lines but not expressed in normal somatic cells, it is thought to contribute to the progressive loss of telomeres with each cell division.

Detailed explanation-2: -Telomerase is not usually active in most somatic cells (cells of the body), but it’s active in germ cells (the cells that make sperm and eggs) and some adult stem cells.

Detailed explanation-3: -In embryonic stem cells, telomerase is activated and maintains telomere length and cellular immortality; however, the level of telomerase activity is low or absent in the majority of stem cells regardless of their proliferative capacity.

Detailed explanation-4: -Telomerase activity is exhibited in gametes and stem and tumor cells. In human somatic cells proliferation potential is strictly limited and senescence follows approximately 50-70 cell divisions. In most tumor cells, on the contrary, replication potential is unlimited.