What are the advantages and disadvantages of the names, principles and processes of the six farming methods?

The six breeding methods include four plants (hybrid breeding, distant hybridization, mutation breeding and molecular breeding) and two animals (hybrid breeding and genetic engineering breeding).

First, cross breeding:

1, principle: gene recombination produces new genotypes and new excellent characters.

2. Process:

2. 1 The preparation before hybridization should first be familiar with the reproductive habits of various fish;

2.2 Choose a suitable fertilization method for hybridization. In the early stage of hybridization, near sexual maturity and breeding season, male and female fish must be raised in separate pools to avoid self-pollination;

2.3 Record, list and manage hybridization with different species (or species) of fish;

2.4 Accelerate the breeding process from hybridization to new variety selection and promotion;

2.5 When the individual selection method is used in the selection of hybrid offspring, the selection generally starts from the second generation, and the second generation has the largest variation range, so it is expected to select a desirable variant from it.

3. Advantages: Two or more excellent traits can be clustered together.

4. Disadvantages: no new genes will be produced, and the hybrid offspring will have character separation, and the breeding process is slow and complicated.

Two: Distant hybridization

1, principle: gene recombination produces new genotypes and new excellent characters.

2. Advantages and disadvantages: We can combine the characteristics and characteristics of different species, break through the boundaries of species and expand genetic variation, thus creating new types of variation or new species. Offspring is a distant hybrid offspring. Because distant hybridization often repeats the evolution of species, it is also an important experimental means to study biological evolution. Distant hybridization is generally not easy to bear fruit Even if it does bear fruit, hybrids are usually sterile or die prematurely, and the separation range of hybrid offspring is large, and the separation generation is long and unstable.

Three: Mutation breeding

1, principle: under artificial conditions, using physical, chemical and other factors, induce biological variation, and cultivate new varieties of animals, plants and microorganisms.

2. Advantages and disadvantages: The main problem of mutation breeding is that the frequency of beneficial mutation is still low, and the direction and nature of mutation are still difficult to control. Therefore, improving the efficiency of mutagenesis, quickly identifying and screening mutants, and exploring ways of directed mutagenesis are important topics in current research.

Four: molecular breeding

1. Principle: Genetic engineering is applied to breeding, and a new variety breeding method is cultivated through gene introduction.

2. Advantages and disadvantages: The traditional breeding method belongs to hybrid breeding, and the variety improvement is mainly limited by the variation of the original species, but the hybridization between different species is quite difficult, and it is difficult to make a big breakthrough in breeding results, and it is difficult for the "green revolution" to happen again. Using genetic engineering technology to improve crop varieties refers to the breeding method of introducing a specific gene or trait into the target crop lacking the gene or trait through genetic engineering technology; Therefore, using genetic engineering technology to improve crop varieties can break through the limitation of seed source and the bottleneck of interspecific hybridization, and create new characters or varieties, that is, the future "genetic revolution" is likely to quickly replace the "green revolution".

Five, genetic engineering breeding

1, principle: gene recombination (or heterologous DNA recombination).

2. Advantages and disadvantages: it is not limited by species and can be carried out purposefully according to human needs. It may cause an ecological crisis and is technically difficult.