The cloned offsprings grow from baby, but later they become old faster and die earlier, why ?
There's many problems with cloning, and I think one of the main problems is to do with imprinting and telomere length. (I'm kind of speculating, because I only skim through the topic when evaluating it for a uni essay, but chose telomerase instead)
Imprinting is where some genes that are normally on (or off) in an adult cell are turned off in gamete cells - which doesn't normally occur with cloned cells. For example, if an adult forms of a protein are produced when a cloned animal is young, it could lead to deteriorated health.
And telomeres are repeats of a nucleotide that capt the ends of all chromosomes, and it prevents chromosomal instabilities. Each time a cell divides, these repeats get shorter. Normally, in gametes, telomerase (a protein) rebuilds the ends of a chromosome. But a nucleus extracted from an adult cell would already have shortened telomeres - possibly reducing life span. I'm sure researchers have found a way around this.. but who knows, perhaps artifically induced telomerase doesn't add enough length.
Hmm.. hopefully all this points you in the right direction... which may be wrong.
I can't recall if the phenomenon of telomere shortening is still considered to be a part of it or not. I seem to recall a debate about that a while back, that it might not account for the premature aging.
I think the bottom line is we don't really know what goes wrong. This is fairly new technology, and a lot of things aren't well understood yet.
Agree with Jikx. A 'true' clone has not been made, at least in higher organisms. The genetic sequence includes a number of active and inactive genes. Not only must the all the genes be in the correct on-off position when cell division is initiated, they must be switched to the correct on-off position at the right time during both embryonic and post-embryonic development. How this 'programming' works is not understood.
Imprinting is a problem, telomeres don't seem to be (last I heard).
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