Animals are often cloned by the method of 'somatic cell nuclear transfer'. suppose, a cow which is about 10 years old is cloned by method of SCNT, its somatic cell nucleus has the genes which already have the information of how old the cow is i.e 10 yrs. now in this method, the complete nucleus of the somatic cell is transfered to an egg-cell of a donor. then this zygote is implanted artificially into another cows womb. After a new calf(clone) is born, will its initial age be 10 years? will its 1st birthday be its 10th birthday? Average lifespan of a cow is about 20 yrs, so will this CLONED COW live only 10 years more? Waiting for input.... Please Register or Log in to view the hidden image!
Cellular aging mechanisms are not my area, but as far as I know a cell primarily keeps a track of its age using the gradually decreasing lengths of the telomeres on its chromosomes. Once a cell’s telomeres shorten to a certain limit, the cell enters senescence. (I’m sure wikipedia will fill you in if you want more info on this.) I don’t know that genes themselves ‘record’ the age of the cell. Genes certainly accumulate mutations over time resulting in a gradual decrease in efficiency and function. Accumulation of mutations in mitochondrial genes results in the gradual loss of energy and slowing metabolism associated with age. Our physiology gradually winds down as a result of the mutation and methylation load on our genome. One of the big questions in SCNT when it was first applied to mammals was whether the process of transplanting a donor nucleus into an enucleated ovum, and the subsequent stimulation of division and embryonic development by specific culturing conditions, would “re-set” the telomeres in the donor nucleus to their original length. It seems that in the first cloned mammal, Dolly in sheep, the answer was no. In other words, the 2-year-old donor nucleus retained its original telomere lengths. So, Dolly’s “cellular age” was 2 years older than her “birth age”. (This had nothing to do with her death.) However, since then many other mammals have been cloned via SCNT and it seems that whether telomeres are re-set by the process varies depending on the species. In some species telomeres in the donor nucleus are restored to their original lengths, thus re-setting the cellular age back to zero. I do not know if this is the case with cows. But, re-setting the cellular age to zero does not mean that the cloned animal is guaranteed to live a normal lifespan as the SCNT process is prone to causing a variety of other developmental problems that result in a shortened lifespan. Cloned animals are prone to cardiovascular, immunological and endocrine abnormalities. Irrespective of the telomere re-setting issue, when cloning a mammal by SCNT, the idea is to use as young an animal as possible as the donor in order to maximise the lifespan of the cloned animal. If cow telomeres are not reset by SCNT, then a cow cloned from a 10 year old donor cell would start life with a cellular age of ~10 years and would likely die about half way through a normal cow lifespan. If cow telomeres are reset by SCNT, then it might live out a normal bovine lifespan if no other cloning-associated problems arise.
Pretty much, yes. It will physically look like a one year old calf on its first birthday, but it's cells will be much older. And yes, cloned organisms don't live as long as the average lifespan of non-cloned members of the same species.
