The core of transgenic animal technology is to transfer the genetic functional unit-gene into animals and make them become a part of animals. The transferred genes can come from the same or different animals, or from plants or microorganisms. In this way, the boundaries between species are broken, and it can be said that animals can cross with plants and microorganisms. However, the current hybridization is at a low level, and only one or two genes are responsible for one or two traits. With the development of science and technology, more and more genetic information can be transmitted at one time, and then the real hybridization between animals and plants can be realized. Scientifically speaking, this will be a great breakthrough.
At present, many methods of producing transgenic animals have been reported in the world, but there are only two methods that are really mature and stable to produce transgenic animals, namely microinjection of DNA and sperm-mediated gene transfer.
The method of microinjection of DNA is gene manipulation of single-cell embryos, which involves complicated operation steps. First of all, it is necessary to accurately grasp the sexual cycle of the female livestock, and on this basis, manually adjust it so that the female livestock can ovulate at a predetermined time and ensure that a large number of newly fertilized single-cell embryos can be obtained. The second step is to collect single-cell embryos by surgical or non-surgical methods, after a short centrifugation, put them under a microscope, inject 500 ~ 600 copies of genes into the nucleus with a glass microtube with a diameter of 1 μ m, and then transplant the embryos injected with DNA into another female animal in the same sexual cycle. After this treatment, 1% ~ 3% transgenic animals will appear in the offspring. Although the efficiency is not high, the result is quite stable. Tens of thousands of experiments have been carried out on various animals all over the world, and transgenic animals can be produced.
Sperm-mediated gene transfer enables sperm to carry foreign genes after proper treatment. Then, sperm carrying foreign genes is used to inseminate female animals in estrus. Among the offspring of female animals, a certain proportion of animals are transgenic animals with foreign genes integrated. Compared with microinjection, sperm-mediated gene transfer has two advantages: first, the cost is very low, which is only110 for microinjection. Secondly, because it does not involve surgical treatment of animals, it can be used to produce cattle or sheep for experiments to ensure the success of each experiment.
Since 1990s, the research on transgenic animal production has become increasingly active. The practical significance of transgenic animal technology lies in: ① cultivating livestock and poultry with excellent characteristics such as fast growth, high fertility and strong disease resistance; (2) using animal body as reactor to produce precious protein, such as protein which can only be extracted from human body; ③ Using animals as research models, for example, knowing that hypertension is caused by some reasons, we can make some hypertensive mice and let doctors try various therapies on them; ④ Making ornamental animals, such as ponies as big as cats, rabbits as big as mice, and ornamental animals with different colors and patterns.
China has also made many gratifying achievements in transgenic animals. At present, transgenic animals such as fish, rabbits and chickens have been obtained. 1In February, 998, scientists in China obtained transgenic goats with protein coagulation factor X in their milk.
Put two mice in a simulated environment and extract all the stress genes of one mouse. Therefore, gray mice without stress genes are always cautious when walking or looking for food. In a simulated natural environment with an area of about 500 square meters, the chinchilla survived for more than ten days without any accident. It even began to store food for the winter and began to get used to this space without human intimidation. Another mouse from which the stress gene was extracted lived in excitement from the beginning. The white mouse swaggered through a space of 500 square meters a day, and it took the gray mouse nearly four days to get familiar with the whole simulated space. The white mouse climbed the rockery with a simulation space as high as 13 meters, while the gray mouse climbed the basket with food only 2 meters high. As a result, on the third day of the simulated space, the mouse climbed the rockery with a height of 13 meters because of no pressure, and fell down and died when trying to pass a small stone. The gray mouse came out alive because of some pressure.