AP BIOLOGY

Detailed explanation-1: -Telomerase has a protein subunit (hTERT) and an RNA subunit (hTR). This enzyme is active in germline and stem cells and maintains their telomere length by adding ‘TTAGGG’ repeats to the ends of chromosomes.

Detailed explanation-2: -Telomeres play a central role in cell fate and aging by adjusting the cellular response to stress and growth stimulation on the basis of previous cell divisions and DNA damage. At least a few hundred nucleotides of telomere repeats must “cap” each chromosome end to avoid activation of DNA repair pathways.

Detailed explanation-3: -An enzyme named telomerase adds bases to the ends of telomeres. In young cells, telomerase keeps telomeres from wearing down too much. But as cells divide repeatedly, there is not enough telomerase, so the telomeres grow shorter and the cells age.

Detailed explanation-4: -Telomeres are structures made from DNA sequences and proteins found at the ends of chromosomes. They cap and protect the end of a chromosome like the end of a shoelace. In almost all animals, from the simplest to the most complex, telomeres are required for cell division.

Detailed explanation-5: -Telomerase is found in high levels in germline? cells (egg and sperm) and stem cells. In these cells telomere length is maintained after DNA replication and the cells do not show signs of ageing. Telomerase is also found in high levels in cancer? cells.