This fact makes the exact cloning of a male a much harder task. Another difference between the clone and the genetic donor is the amount of cytoplasm present in the first chimeric cell. The combining of the cells adds their cytoplasm and its contents to form the new cell. It is unknown how this difference could affect the growth of an individual at such an early stage. Studies on Dolly's DNA have also shown that the telomeres of her chromosomes are shorter than those of the genetic donor's.
Telomeres become gradually shorter with every somatic cell replication.
This shortening may be what eventually causes cell death and aging. Some researchers have suggested the possibility of mtDNA being responsible for aging. In a few years, it may be found that Dolly and the other mammalian clones age prematurely. There are even more problems with cloning humans. The development of the human brain depends heavily on the physical stimulants it receives early in life.