Depending on the methods and objects of foreign gene introduction, the main methods for producing transgenic animals include microinjection, retrovirus, embryonic stem cell (ES cell) method, and electroporation. Pulse method, sperm carrier introduction method, etc.
1. Microinjection
is the most commonly used method with a high success rate. The characteristic of gene microinjection method is that the introduction and integration efficiency of foreign genes is high, no vector is needed, and the target gene can be directly transferred, and the length of the target gene can reach 100kb (100,000 base pairs).
It can directly obtain pure strains, so the experimental period is short. However, it requires expensive precision instruments and is difficult to operate technically. Moreover, the integration site and integrated copy number of foreign genes cannot be controlled, which can easily cause insertion mutations in the genome of the host animal, causing corresponding changes in traits, and in worst cases, death.
2. Retrovirus infection method
This method has a high integration rate and the target gene is not easy to destroy. It is mostly a single copy and single point integration, which is suitable for cases where it is difficult to observe the pronucleus. Fertilized poultry eggs. Due to the limitation of the size of the virus capsid, the target gene should not exceed 10kb, otherwise the activity and stability will be affected. In addition, viral DNA may affect the expression of foreign genes in the host animal.
3. Embryonic stem cell method
Embryonic stem cells (ES cells) refer to undifferentiated embryonic cells isolated from the inner cell mass of the blastocyst stage. They have developmental totipotency and can Carry out in vitro culture; genetic operations such as amplification, transformation and production of genetic mutants.
This method has a high integration rate of exogenous genes and selects suitable transformed ES cells before implantation into the blastocyst, overcoming the previous shortcomings of only selecting in offspring and making full use of molecular biology for development. Various advanced methods are promising technologies. The disadvantage is that it is difficult to establish ES cell lines. And because it is through the chimera approach, the experimental cycle is long.
4. Electric pulse method
Electropulse method (electroporation), also known as electroporation method, is to fully mix the donor DNA and the recipient cells, and expose them to high external voltage for a short period of time. The cell membrane structure is changed under the pulse, causing instantaneous reversible electroporation of the cell membrane, so that DNA of a certain size can enter the cell through the cell membrane and be transported to the nucleus.
5. Sperm introduction method
Using sperm as a foreign gene carrier, the foreign gene is introduced into the fertilized egg through fertilization and integrated into the genome of the fertilized egg, which is called sperm. The vector introduction method is a new attempt to construct transgenic animals.
This method is simple and convenient. It relies on the physiological adsorption process and avoids damage to the pronucleus. However, the success rate is low in practice, and there is controversy over whether sperm can be used as a carrier of foreign DNA. This technology is still in the exploratory stage. This method can combine artificial insemination, in vitro fertilization and genetic modification.
Safety Management
In my country, laws and regulations such as the "Regulations on the Safety Management of Agricultural Genetically Modified Organisms" and the "Measures for the Safety Evaluation and Management of Agricultural Genetically Modified Organisms" have been promulgated. A series of regulations have been made in terms of management scope, safety evaluation, management measures, etc. to ensure safe use.
Genetically modified technology is leading a new agricultural technology revolution. The Chinese public still has some doubts about genetically modified technology and genetically modified foods. Various forms of education should be used to popularize life science knowledge so that the public has a more scientific understanding of genetically modified technology and actively accept genetically modified foods. Bring genetically modified technology closer to the people and benefit mankind.
Reference for the above content: Baidu Encyclopedia - Transgenic Animals, Baidu Encyclopedia - Animal Transgenic Technology