Well, the hard part is how to protect the ends of this line. Because you could imagine that if you didn't protect them they would become ragged, and maybe there'd be little parts of them that would be lost. So the telomeres are special DNA that sit at the end of the chromosome that have repetitive sequences that are recognized as the end of the chromosome, but they keep the chromosome from becoming frazzled or damaged . And every time the cell divides, the telomeres also divide. But sometimes they can become shorter. And as they become shorter, that's a clock that the cell is counting to know how old it is, and that will limit how many times the cell can divide without losing some of the important DNA on the chromosome. And one of the interesting features that's understood now about telomeres is that in cancer cells, which have a more infinite capacity for self-division, one of the important changes that they make is that they keep their telomeres long, so that molecular clock goes away and those cells can keep dividing, even though they should get to the end of their lifespan. And that's one of the ways in which the cancer cells basically trick the human body into thinking that they should still keep replicating.
Telomere. Telomere. =. A telomere is the end of a chromosome. Telomeres are made of repetitive sequences of non-coding DNA that protect the chromosome from damage. Each time a cell divides, the telomeres become shorter. Eventually, the telomeres become so short that the cell can no longer divide.
So the telomeres are special DNA that sit at the end of the chromosome that have repetitive sequences that are recognized as the end of the chromosome, but they keep the chromosome from becoming frazzled or damaged. And every time the cell divides, the telomeres also divide. But sometimes they can become shorter.
When the telomere becomes too short, the chromosome reaches a ‘critical length’ and can no longer be replicated.
Telomere biology is incredibly important in human cancer and scientists are working hard to understand the best way to exploit their knowledge of it to advance the treatment of cancer.
Telomeres and telomerase present a number of potential targets for the design of new cancer therapies. Cancer cells contain active telomerase to enable them to become ‘immortal’ and continue dividing uncontrolled. Cancer is a disease characterised by the rapid and uncontrolled division of cells. Without telomerase activity, these cells would become ...
The medical relevance of telomeres is uncertain. Human cells cultured in the lab have been observed to stop dividing when telomerase is inactivated, because the length of telomeres is not maintained after cell division. The cells then enter a state of inactivity called senescence. However, once telomerase is reactivated, ...
Telomerase? is an enzyme? that adds the TTAGGG telomere sequence to the ends of chromosomes. Telomerase is only found in very low concentrations in our somatic cells?. Because these cells do not regularly use telomerase they age leading to a reduction in normal function. The result of ageing cells, is an ageing body.
They consist of the same sequence of bases ? repeated over and over. In humans the telomere sequence is TTAGGG. This sequence is usually repeated about 3,000 times and can reach up to 15,000 base pairs? in length.
Every time a cell? carries out DNA replication? the chromosomes are shortened by about 25-200 bases (A, C, G, or T) per replication. However, because the ends are protected by telomeres, the only part of the chromosome that is lost, is the telomere, and the DNA is left undamaged.
telomerase adds DNA nucleotides to the overhang and DNA polymerase extends the complimentary strand.
1. Chromosome stability- protect the ends of chromosomes.
When telomeres are or become very short, cells can no longer divide effectively. When this problem is systemic, it can result in a range of telomere biology disorders (TBDs), also known as short telomere syndromes or telomeropathies.
As genetic material is replicated, and cells divide, telomeres are naturally depleted. Without telomerase to synthesize additional DNA repeats, the telomeres continually shorten, until ultimately, they are critically short and initiate cell senescence or death.
Telomerase is absent or only present at very low levels in most human cells. It is thought that telomerase is restricted as a mechanism to impose a limit on cell proliferation. This can act as an anti-tumor protective mechanism.
Telomerase is an enzyme whose main function is the maintenance of telomeres. Here we examine what the purpose of telomerase is and the impact when it doesn’t work as it should.
Telomerase was discovered and named in 1985 by Carol Greider and Elizabeth Blackburn, earning them shares, along with Jack Szostak, in the 2009 Nobel Prize for Physiology or Medicine. You can read more about their discovery here.
Telomerase is also upregulated in most cancer cells, reflecting the need for telomere maintenance for highly active cell division and tumor development.