What Would Be The Consequence Of A Chromosome Losing Both Of Its Telomeres In An Animal Cell?

Telomeres are distinctive structures found at the ends of our chromosomes. They consist of the same curt DNA sequence repeated over and over again.

Telomeres are sections of DNA found at the ends of each of our chromosomes.
They consist of the same sequence of bases repeated over and over.
In humans the telomere sequence is TTAGGG.
This sequence is normally repeated about 3,000 times and can attain up to xv,000 base pairs in length.

Illustration showing the position of telomeres at the end of our chromosomes.

Illustration showing the position of telomeres at the end of our chromosomes.
Image credit: Genome Research Limited

What exercise telomeres do?

Telomeres serve 3 major purposes:

They help to organise each of our 46 chromosomes in the nucleus (command middle) of our cells.
They protect the ends of our chromosomes by forming a cap, much like the plastic tip on shoelaces. If the telomeres were not there, our chromosomes may end up sticking to other chromosomes.
They allow the chromosome to be replicated properly during cell division:
- Every fourth dimension a prison cell carries out DNA replication the chromosomes are shortened by near 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.
- Without telomeres, of import DNA would exist lost every fourth dimension a cell divides (usually about 50 to lxx times).
- This would somewhen lead to the loss of entire genes.

Each time a cell divides, 25-200 bases are lost from the ends of the telomeres on each chromosome.
2 master factors contribute to telomere shortening during jail cell division:
- The "finish replication problem" during Dna replication: Accounts for the loss of well-nigh 20 base pairs per cell division.
- Oxidative stress: Accounts for the loss of between 50-100 base of operations pairs per cell division. The amount of oxidative stress in the trunk is thought to be afflicted by lifestyle factors such as diet, smoking and stress.
When the telomere becomes too short, the chromosome reaches a 'critical length' and tin no longer exist replicated.
This 'critical length' triggers the jail cell to die by a process called apoptosis, as well known as programmed cell death.

Telomerase is an enzyme that adds the TTAGGG telomere sequence to the ends of chromosomes.
Telomerase is only found in very depression concentrations in our somatic cells. Because these cells do not regularly apply telomerase they age leading to a reduction in normal office.
The result of ageing cells, is an ageing torso.
Telomerase is found in high levels in germline cells (egg and sperm) and stem cells. In these cells telomere length is maintained after Deoxyribonucleic acid replication and the cells do non bear witness signs of ageing.
Telomerase is besides plant in high levels in cancer cells. This enables cancer cells to exist immortal and continue replicating themselves. If telomerase activity was switched off in cancer cells, their telomeres would shorten until they reached a 'critical length'. This would, prevent the cancer cells from dividing uncontrollably to form tumours.
The activity of telomerase allows cells to go along multiplying and avoid ageing.

Telomere caps

Epitome credit: U.S. Department of Energy Human Genome Program. Licensed under Public domain via Wikimedia Commons.

Inquiry on telomeres and the part of telomerase could uncover valuable information to combat ageing and fight cancer.
The medical relevance of telomeres is uncertain.
Human cells cultured in the lab take been observed to end dividing when telomerase is inactivated, because the length of telomeres is non maintained after cell division.
The cells and then enter a state of inactivity called senescence. However, once telomerase is reactivated, the cells are able to continue dividing.
If telomerase tin can be used to help human cells live forever, it may also be possible to mass produce cells for transplantation. These cells could help to care for a range of conditions, from severe burns to diabetes.

Telomeres and ageing

Mice models lacking the enzyme telomerase were constitute to testify signs of premature ageing.
However, it is not certain whether telomere shortening is responsible for ageing in humans or whether it is just a sign of ageing, like grayness hair.
There are several indications that telomere length is a good predictor of lifespan.
Newborn babies tend to have telomeres ranging in length from around 8,000 to 13,000 base pairs. It has been observed that this number tends to decline by effectually 20-40 base pairs each year. So, by the fourth dimension someone is twoscore years one-time they could have lost up to i,600 base pairs from their telomeres.
Even so, looking at the bigger moving picture, the overall shortening of our telomeres is not meaning, even in very old people.
Cells that divide rapidly, such as germ cells and stem cells, are among the few jail cell types in our bodies containing agile telomerase.
This means that in these cells telomere length is maintained or even lengthened over time.
However, in that location are a number of other factors that have an effect on the length of our telomeres that all demand to be considered, such as smoking and obesity.

Telomeres and 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 illness characterised by the rapid and uncontrolled segmentation of cells.
Without telomerase activity, these cells would become inactive, end dividing and eventually die.
Drugs that inhibit telomerase activity, or kill telomerase-producing cells, may potentially stop and kill cancer cells in their tracks.
However, blocking telomerase activeness could affect cells where telomerase activity is important, such as sperm, eggs, platelets and immune cells.
Disrupting telomerase in these cell types could affect fertility, wound healing and the ability to fight infections.
All the same, telomerase activity in somatic cells is very low. These cells would therefore be largely unaffected past anti-telomerase therapy.
Scientists hope this would upshot in fewer side effects for the patient, compared to current cancer therapies.
Telomere biology is incredibly important in human cancer and scientists are working hard to understand the all-time way to exploit their knowledge of it to advance the handling of cancer.

This page was last updated on 2021-07-21

Source: https://www.yourgenome.org/facts/what-is-a-telomere