TelomeresWhat are they?What are they for?How can we use them?

What are Telomeres?• Telomeres are the sections of DNA found at the

ends of the chromosomes. • They are often compared to shoelace tips.• This is because they keep chromosome ends

from fraying and sticking to each other, which would destroy or scramble an organism's genetic information.

• Telomeres are made of repeating sequences of TTAGGG on one strand paired with AATCCC on the other strand.

• Thus, one section of telomere is a "repeat" made of six base pairs.

• In white blood cells, the length of telomeres ranges from 8,000 base pairs in new-borns to 3,000 base pairs in adults and as low as 1,500 in elderly people.

• The average chromosome contains 150m pairs.

Telomeres and Ageing• Each time a cell divides, it loses 30 to 200 base

pairs from the ends of its telomeres.• Cells normally can divide only about 50 to 70

times, with telomeres getting progressively shorter until the cells no longer divide and die.

• This is due to the way in which semi conservative DNA replication is carried out.

• Telomeres prevent sections of DNA from being missed out in replication.

Telomerase• Telomerase is the enzyme that is responsible for

building the telomeres back up. This enzyme is particularly present in young cells.

• But as cells divide, telomerase levels decrease, to the point where the telomeres are no longer built back up.

• This limited supply of telomerase makes our cells mortal.

structure of the catalytic subunit of telomerase

Telomeres and Cancer• As cells become cancerous they divide

uncontrollably. If these cells had limited telomerase, then they should soon age and die.

• However, many cancer cells are able to produce more telomerase, thus making them immortal.

• In the future, measuring telomerase levels may be a way to detect cancer.

• In one experiment, researchers blocked telomerase activity in human breast and prostate cancer cells growing in the laboratory, prompting the tumour cells to die.

• However there are risks. Blocking telomerase could impair fertility, wound healing, and production of blood cells and immune system cells.

Telomerase and Immortality?• If telomerase can make cancer cells immortal,

why not us?• Could we extend lifespan by preserving or

restoring the length of telomeres with telomerase?

• Scientists have been able to use telomerase in human cells in a lab to allow the cells to divide far beyond the normal limit.

• However, the risk of this is that there is a possibility of uncontrollable division leading to cancers.

• If we used Telomerase to "immortalize" human cells, we may be able to mass produce cells for transplantation.

• For example insulin producing cells to cure diabetes.

• Muscle cells for treating muscular dystrophy.• Cartilage for arthritis.• Skin cells for skin grafts and facial

reconstruction.

• An unlimited supply of human cells would also aid in the testing of new drugs and gene therapies.

Are Telomeres the Whole Story?• Telomeres are not the sole contributors to the

process of ageing, there are multiple factors involved.• This doesn’t mean however, that telomerase couldn’t

greatly expand our life expectancy.

• The most important cause of ageing in damage from oxidants/free radicals that are created in respiration and other processes. Oxidant are also produced in the consumption of alcohol and cigarettes.

• In one study, scientists exposed worms to two substances that neutralize oxidants, and the worms' lifespan increased an average 44%.