(2) Differences in environmental safety between transgenic plants and recipient or parent plants:
The effects of transgenic plants resistant to pests and diseases on target and non-target organisms, including their effects on beneficial and harmful organisms in the environment.
Other beneficial or harmful effects of genetically modified plants on the ecological environment
(3) Differences in the effects of transgenic plants on human health compared to recipient or parent plants:
Toxicity of genetically modified plants
Allergenicity of genetically modified plants
Transgenic plant antinutritional factors
Genetically modified plant nutrients
Transgenic plants for antibiotic resistance
Other impacts of genetically modified plants on human health and food safety
(4) Based on the above evaluation, the safety level of genetically modified plants is classified in accordance with relevant laws and regulations.
IV. Safety Assessment of Genetically Modified Plant Products
(1) The impact of production and processing activities on the safety of genetically modified plants.
(2) Stability of genetically modified plant products.
(3) Differences in environmental safety between genetically modified plant products and genetically modified plants.
(4) Differences between the effects of genetically modified plant products and genetically modified plants on human health.
(5) The safety levels of genetically modified plant products shall be classified according to the above results and relevant regulations.
What are the types of genetic markers? What are their characteristics?
Morphological mark: a type of appearance feature that can be clearly observed with the naked eye
Source of materials: natural mutation; physical and chemical mutagenesis
Advantages: Simple and intuitive, economical and convenient, and easy to observe and record. Based on morphological markers located on a specific chromosome segment, linkage analysis can be performed on other unlocated genes (or mutant traits). By hybridizing materials with different marker genes and selecting materials with multiple marker segregation, two-point and three-point linkage tests can be used to determine the relationship between the gene and the target trait.
Limitations: Small number of morphological markers and limited identifiable marker genes make it difficult to establish a saturated genetic map; many morphological markers are also affected by factors such as environment and growth period; some morphological markers have a significant impact on plant phenotypes and are linked to undesirable traits
Cytological markers: Cytological characteristics that can clearly show genetic polymorphisms
Abnormalities in chromosome structure and number often lead to abnormalities in certain phenotypic traits. Chromosome changes can be used as a genetic marker.
Applications: Tomato trisomy, tobacco monosomy, maize BA translocation lines, rice primary trisomy, wheat complete monosomy, telomeres, and null-tetrasomy, cotton translocation lines
Limitations: Requires significant manpower and time for identification and cultivation; some species are sensitive to variations in chromosome number and structure, have poor adaptability to variation, and are difficult to preserve; some traits that do not involve variations in chromosome number, structure, or banding patterns are difficult to detect using cytological methods; using aneuploidy for mapping can locate genes to a specific chromosome, but it is difficult to conduct precise gene mapping; the number of available cytological markers is limited.
Biochemical markers: a type of genetic marker system based on the protein products of gene expression
Mainly includes storage protein (non-enzyme protein), isoenzyme (enzyme protein) and other markers
Isozyme characteristics: having the same function but different structure and composition, genetic behavior conforming to Mendel's law, co-dominant expression, and polymorphism
Advantages of isoenzyme applications: analysis can be performed directly on small samples of tissues and organs; proteins are products of gene expression and can directly reflect differences in gene products; nearly 70 enzyme detection systems have been developed for legumes, which can identify approximately 100 gene loci. Nearly 160 polymorphic isoenzyme loci have been identified in crops such as rice.
Disadvantages of isozyme application: The number of isozyme markers available is limited, which is insufficient for most crops.
30; Few isoenzyme types and alleles exhibit polymorphism; Each isoenzyme marker requires a specific colorimetric method and technique; The activity of some enzymes is developmental and tissue specific; Isoenzyme markers are limited to reflecting expression information in the coding regions of the genome
DNA molecular markers: genetic polymorphisms at the DNA level
Applications: Germplasm resource research, system analysis, variety registration and patent protection, genetic map construction, gene mapping, molecular marker-assisted selection
Advantages: They are directly expressed in the form of DNA and can be detected in all tissues and developmental stages of the plant body. They are not restricted by the environment and there is no problem of whether they are expressed or not. There are many of them, covering the entire genome, and the detection sites are almost infinite. They are highly polymorphic, and there are many allelic variations in nature, so there is no need to create special genetic materials. They are "neutral", that is, they do not affect the expression of target traits and are not necessarily linked to adverse traits. Many molecular markers are co-dominant, which can identify homozygous genotypes and heterozygous genotypes and provide complete genetic information.
What categories can DNA molecular markers be divided into?
(1) Molecular markers based on DNA-DNA hybridization
(2) Molecular markers based on PCR technology
(3) Molecular markers based on a combination of PCR and restriction enzyme digestion
(4) Molecular markers based on DNA chip hybridization technology
(5) Molecular markers targeting specific domains
(6) High-throughput molecular labeling
3. Describe the principles and characteristics of restriction-length polymorphism (RFLP) markers and the basic steps for developing RFLP markers.
Principle: (1) Use specific restriction endonucleases to digest the genomic DNA of different organisms. The number of DNA fragments produced and the length of each fragment reflect the distribution of different restriction endonucleases on the DNA molecule.
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