2014年9月20日 星期六

aging, telomeres . chromosome

 If you are unfamiliar with the componentry of your genes, telomeres are the tiny caps on the ends of DNA strands. They shorten and fray as a cell ages, although the process is not strictly chronological. Obesity, illness and other conditions can accelerate the shortening, causing cells to age prematurely, while some evidence suggests that healthy lifestyles may preserve telomere length, delaying cell aging.

Ageing is a daunting process, not least because some of the first things to fail are also the most useful, such as memory, attention and motor skills. The idea that some form of regular mental activity can postpone mental decline is not new. Now researchers have found another: playing a certain type of video game could help the elderly stay sharper for longer http://econ.st/1em4h7X

Nobel prize for chromosome find

Chromosomes house genetic material

This year's Nobel prize for medicine goes to three US-based researchers who discovered how the body protects the chromosomes housing vital genetic code.
Elizabeth Blackburn, Carol Greider and Jack Szostak jointly share the award.
Their work revealed how the chromosomes can be copied and has helped further our understanding on human ageing, cancer and stem cells.
The answer lies at the ends of the chromosomes - the telomeres - and in an enzyme that forms them - telomerase.


The 46 chromosomes contain our genome written in the code of life - DNA.
When a cell is about to divide, the DNA molecules, housed on two strands, are copied.
But scientists had been baffled by an anomaly.
For one of the two DNA strands, a problem exists in that the very end of the strand cannot be copied.
Protecting the code of life
Therefore, the chromosomes should be shortened every time a cell divides - but in fact that is not usually the case.
If the telomeres did repeatedly shorten, cells would rapidly age.

 The discoveries ... have added a new dimension to our understanding of the cell, shed light on disease mechanisms, and stimulated the development of potential new therapies
The Nobel Assembly

Conversely, if the telomere length is maintained, the cell would have eternal life, which could also be problematic. This happens in the case of cancer cells.
This year's prize winners solved the conundrum when they discovered how the telomere functions and found the enzyme that copies it.
Elizabeth Blackburn, of the University of California, San Francisco, and Jack Szostak, of Harvard Medical School, discovered that a unique DNA sequence in the telomeres protects the chromosomes from degradation.
Joined by Johns Hopkins University's Carol Greider, then a graduate student, Blackburn started to investigate how the teleomeres themselves were made and the pair went on to discover telomerase - the enzyme that enables DNA polymerases to copy the entire length of the chromosome without missing the very end portion.
Their research has led others to hunt for new ways to cure cancer.
It is hoped that cancer might be treated by eradicating telomerase. Several studies are under way in this area, including clinical trials evaluating vaccines directed against cells with elevated telomerase activity.
Some inherited diseases are now known to be caused by telomerase defects, including certain forms of anaemia in which there is insufficient cell divisions in the stem cells of the bone marrow.
The Nobel Assembly at Sweden's Karolinska Institute, which awarded the prize, said: "The discoveries... have added a new dimension to our understanding of the cell, shed light on disease mechanisms, and stimulated the development of potential new therapies."
Carol Greider, now 48, said she was phoned in the early hours with the news that she had won.
She said: "It's really very thrilling, it's something you can't expect."
Elizabeth Blackburn, now 60, shared her excitement, saying: "Prizes are always a nice thing. It doesn't change the research per se, of course, but it's lovely to have the recognition and share it with Carol Greider and Jack Szostak."
Professor Roger Reddel of the Children's Medical Research Institute in Sydney, Australia, said: "The telomerase story is an outstanding illustration of the value of basic research."
Sir Leszek Borysiewicz, chief executive of the Medical Research Council, said: "The Medical Research Council extends its congratulations to Blackburn, Greider and Szostak on winning the 2009 Nobel Prize.
"Their research on chromosomes helped lay the foundations of future work on cancer, stem cells and even human ageing, research areas that continue to be of huge importance to the scientists MRC funds and to the many people who will ultimately benefit from the discoveries they make."


Line breaks: telo|mere
Pronunciation: /ˈtiːlə(ʊ)mɪə
, ˈtɛl-/


A compound structure at the end of a chromosome.


1940s: from Greek telos 'end' + meros 'part'.





Line breaks: chromo|some 染色體

Pronunciation: /ˈkrəʊməsəʊm 


A thread-like structure of nucleic acids and protein found in the nucleus of most living cells, carrying genetic information in the form of genes.
Each chromosome consists of a DNA double helix bearing a linear sequence of genes, coiled and recoiled around aggregated proteins (histones). Their number varies from species to species: humans have 22 pairs plus the two sex chromosomes (two X chromosomes in females, one X and one Y in males). During cell division each DNA strand is duplicated, and the chromosomes condense to become visible as distinct pairs of chromatids joined at the centromere


late 19th century: coined in German from Greek khrōma'colour' + sōma 'body'.


Syllabification: (age)
Pronunciation: /āj/
Translate age | into French | into German | into Italian | into Spanish


  •  1the length of time that a person has lived or a thing has existed:he died from a heart attack at the age of 51 his wife is the same age as Carla he must be nearly 40 years of age young people between the ages of 11 and 18
  •  a particular stage in someone’s life:children of primary school age
  •  the latter part of life or existence; old age:with age this gland can become sluggish
  •  2a distinct period of history:an age of technological growth a child of the television age
  •  Geology a division of time that is a subdivision of an epoch, corresponding to a stage in chronostratigraphy.
  •  archaic a lifetime taken as a measure of time; a generation:Nestor is said to have lived three ages when he was ninety years old
  •  (ages/an ageinformal a very long time:I haven’t seen her for ages it would take an age to tell her everything

verb (agesageing or agingaged)

[no object]
  •  grow old or older, especially visibly and obviously so:you haven’t aged a lot the tiredness we feel as we age
  •  [with object] cause to grow, feel, or appear older:he even tried aging the painting with a spoonful of coffee
  •  (especially with reference to an alcoholic drink) mature or allow to mature: [no object]:the wine ages in open vats or casks
  •  [with object] determine how old (something) is:we didn’t have a clue how to age these animals


act (or be) one's age

[usually in imperative] behave in a manner appropriate to someone of one’s age and not to someone much younger:“Act your age” is not advice to behave like an adolescent

come of age

(of a person) reach adult status.
(of a movement or activity) become fully established:space travel will then finally come of age

of an age

  •  1old enough to be able or expected to do something:the sons are of an age to marry
  •  2(of two or more people or things) of a similar age:the children all seemed of an age

through the ages

throughout history.


Middle English: from Old French, based on Latin aetasaetat-, from aevum 'age, era'

Spelling help

Aging is usually spelled without an e, although ageing is also correct.