British scientists have developed a new type of transgenic cloned sheep (6.30)

OA show ('918 '); scientists from the British ppl company, which once bred dolly sheep, reported in the British journal Nature published on the 29th that they have successfully bred two transgenic cloned sheep using precise gene mapping technology, thus opening a new way for the effective transformation of mammalian specific genes The two ewes, named "Diana" and "Cupid", were cloned from mature cells and contained human genes controlling the production of "1-antitrypsin" Their milk juice contains a lot of "1-antitrypsin" Before that, scientists have also produced many transgenic mammals For example, ppl introduced the genetically modified sheep "Polly" to the outside world in 1997 Its milk contains human coagulation factors that can treat hemophilia However, the efficiency of breeding these transgenic animals is very low, because when the cells are implanted with foreign DNA (deoxyribonucleic acid) fragments, due to the inaccuracy of positioning, the DNA fragments often fall on the wrong areas of the chromosome In order to achieve the desired effect of gene transformation, researchers have to repeat the experiment constantly It's like a football player shooting with his eyes covered, hoping to hit it once in a while Using gene mapping technology, Alexander king, a ppl scientist, successfully implanted human chromosome fragments into specific regions of sheep cell chromosomes Then they used the nuclear transfer technology of Dolly, a sheep breeding clone, to combine the modified nucleus with the nucleus removed egg, and cloned 12 lambs through surrogate mothers But only three of them survived, and only "Diana" and "Cupid" showed the characteristics after the correct transformation Ron James, general manager of the company, said that on the basis of the research, scientists are expected to eliminate and close the genes of various animals, so as to cultivate various transgenic animals with high efficiency For example, to eliminate the genes that produce toxic protein in the body of cattle, so that cattle can avoid the risk of mad cow disease, or to eliminate the genes of substances that cause rejection reactions in the body of animals, so that animal organs can be transplanted to people smoothly China feed industry information network a3s (author:)