Comment Dolly and Telomeres (Score 4) 99
What is happening to Dolly's clones is a predictable event and one which did not surprise me at all. It simply proves a point.
Eucaryotes(aka multicellular life forms) have linear Chromosomes as opposed to prokaryotes(bacteria) which have circular chromosomes. Each time a linear chromasome replicates thru cell division, it losses some of its ends. This is called degenerate replication. An enzyme with an RNA core (used as a template) is used by the cell to replace the bases that can not be replicated and it is called Telomerase. The strech of DNA that is shortening is called the Telemere. Normally, telomerase is NOT active in cells other than in very early life(before the 2nd trimester). Although it has been found in some cells in the adult. Those cells are believed to be the pluripotent stem cells(capable of forming just about any cell in the body) and CANCER cells. If a cell wants to live forever, telomerase will have to reawaken and repair its ends if it does not, the belief in the scientific community is that the cell will undergo "Programmed death" (aka apoptosis) when the telemeres on the ends of the chromosome gets to short. An example of this principle can be seen in the disease ATAXIA TELANGIESIA (AT). These poor souls are born with abherently short telomeres and by the age of 18, the individuals resemble a 70 year old.
With that said, the DNA that was used for Dolly's clones was obtained from the breast of Dolly and the cells were fully differentiated and thus had already undergone significant shortening of the chromosome before the DNA was harvested. One would expect several things to happen. 1) DNA will age faster due to telemeric shortening and 2) DNA will have acumulated mutations from Dolly's life as well as from its own life and thus will have a higher disposition for cancer. I define cancer as the acuumulation of mutations that allows for genes to be disregulated and thus cells live when they should die. We have cells in our lab that were harvested from a lady named Helen ~30 years ago(Hela cells) and they are still alive and kicking while Helen is not. This cells are very screwed up(>90 chromasomes) and they have active telmerase.
Eucaryotes(aka multicellular life forms) have linear Chromosomes as opposed to prokaryotes(bacteria) which have circular chromosomes. Each time a linear chromasome replicates thru cell division, it losses some of its ends. This is called degenerate replication. An enzyme with an RNA core (used as a template) is used by the cell to replace the bases that can not be replicated and it is called Telomerase. The strech of DNA that is shortening is called the Telemere. Normally, telomerase is NOT active in cells other than in very early life(before the 2nd trimester). Although it has been found in some cells in the adult. Those cells are believed to be the pluripotent stem cells(capable of forming just about any cell in the body) and CANCER cells. If a cell wants to live forever, telomerase will have to reawaken and repair its ends if it does not, the belief in the scientific community is that the cell will undergo "Programmed death" (aka apoptosis) when the telemeres on the ends of the chromosome gets to short. An example of this principle can be seen in the disease ATAXIA TELANGIESIA (AT). These poor souls are born with abherently short telomeres and by the age of 18, the individuals resemble a 70 year old.
With that said, the DNA that was used for Dolly's clones was obtained from the breast of Dolly and the cells were fully differentiated and thus had already undergone significant shortening of the chromosome before the DNA was harvested. One would expect several things to happen. 1) DNA will age faster due to telemeric shortening and 2) DNA will have acumulated mutations from Dolly's life as well as from its own life and thus will have a higher disposition for cancer. I define cancer as the acuumulation of mutations that allows for genes to be disregulated and thus cells live when they should die. We have cells in our lab that were harvested from a lady named Helen ~30 years ago(Hela cells) and they are still alive and kicking while Helen is not. This cells are very screwed up(>90 chromasomes) and they have active telmerase.
