Twenty years ago, Dolly the cloned sheep became the first mammal successfully cloned by somatic cell nuclear transfer (SCNT), which became an important milestone in life science. However, Dolly's "sheep birth" was not particularly smooth. When she was six and a half years old, she had to be euthanized early because of severe pneumonia and osteoarthritis (sheep of the same breed as her usually live for about ten years).
With regard to Dolly's premature aging, many scientists believe that the telomere in cloned animal cells (that is, the terminal part of chromosome, which will be shortened every time the cell divides) inherited the telomere length of the somatic cell of the donor adult sheep (about six years old at that time), that is to say, Dolly's chromosome "inherited" the donor's age, thus affecting her life span. When Dolly was young, people also took blood tests and confirmed that telomere length was indeed shorter than that of sheep of the same age, which seemed to confirm this conjecture. This casts a shadow over the prospect of cloning technology, and also becomes the theoretical basis for the short life span of cloned people in many science fiction works.
However, an experimental team later found that cloned cattle would repair telomeres during embryonic development, and the length after repair could reach the level of other animals of the same age, which seems to mean that cloned animals may hope to get rid of the short-lived curse. A recently published paper shows that cloned sheep can also lead a normal "sheep life".
In this paper published in the latest issue (July 25th) of Nature News, a research team headed by Professor Sinclair of Nottingham University reported the health status of thirteen cloned sheep. These sheep are seven to nine years old, and four of them are from the same breast cell line as Dolly (that is, they are her "cloned sisters" and have the same genetic information as Dolly). They are eight years old this year.
The researchers tested several physical indexes (metabolism, cardiovascular system and exercise system) of these sheep, which are often used to measure the aging degree of sheep. The results showed that the blood pressure of these sheep was normal, there was no diabetes, the indexes were not much different from those of the control group, and the symptoms of osteoarthritis were very mild (most sheep could only find traces of osteoarthritis under X-ray, without any clinical manifestations). In other words, from the test results, these sheep are not much different from ordinary sheep.
Because accurate telomere measurement needs to wait until the sheep is dead to detect its organs, there is no telomere-related data in this paper. But the researchers say that these sheep are in very good health and are likely to continue to live a healthy life. Sheep will be euthanized according to the experimental plan after they reach the age of 10 for further study and confirmation.
This study is expected to restore people's confidence in animal cloning technology and make people seriously consider its application prospects (for example, cloning technology may increase the number of endangered animals). In addition, in any future works, if there is a short life span of clones, it is the author's problem.
News link:
/science/2065 438+06/07/the-normal-boring-life-of-a-clone-dollys-cloned-croft-hits-age/
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