How is the genetics of laboratory animals classified?
实验动物,遗传学
z-bo
2020-07-24
619
1. Genetic classification
From the point of view of genetics, laboratory animals are genetically restricted animals. According to different genetic characteristics, the experimental animals are divided into inbred, closed and hybrid groups. According to the degree of homozygous gene, experimental animals can be divided into two types, the same genotype and different genotypes. The same genotype includes inbred strains, mutant strains and hybrid F1 generation animals (they are strictly inbred strains with mutant genes) and hybrid F1 generation animals. Belonging to different genotypes, including heterozygous group and closed group of other animal groups, except for hybrid F1 generation animals. When a closed group has a specific mutant gene, it is called a mutant. Generally speaking, the biological characteristics of individuals in inbred, mutant and hybrid F1 animal populations are very consistent, while the biological characteristics of individuals in closed populations are completely different. Inbred animals also include normal inbred lines, recombinant inbred lines, recombinant homologs, homologous mutant inbred lines, homologous inbred lines, and so on. A large amount of data shows that animals of different genotypes have obvious differences in biological characteristics, and their responses to external stimuli are also different. For example, in inbred BALB/c mice of the same age anatomically, BALB/c mice have larger spine, more brain weight/body weight, and heavier spleen and thymus than A mice . With the development of biotechnology, new types of experimental animals such as chimeric animals, uniparental homozygous diploid animals and transgenic animals continue to emerge. These animals cannot simply fall into the above categories, but must be based on their respective inheritance. Components can be combined together or combined separately. For example, uniparental homozygous diploid animals can be classified as inbred, while chimeric animals can only be classified as one category. Due to different genetic backgrounds and transgenic technologies, transgenic animals have different genetic composition, but there is currently no clear classification method, and they are classified as transgenic animals.
2. The concept of breed and strain of experimental animals
1. Species are the most basic unit of biological classification. Species are groups of similar natural groups that can cross each other. Reproductive isolation from other groups. There may be smaller categories under a species, such as species and strains. In the laboratory animal classification system, species and strains are the basic classification units.
2. Breed usually refers to a group of animals that are easy to identify, have certain characteristics that people need, and are basically heritable. New Zealand White Rabbit, Purple Blue Rabbit, Wistar Mouse, KM Mouse, etc.
3. In experimental zoology, animals that are highly genetically homozygous are called "working animals." For example, C57BL/6 is an inbred line, belonging to the low-cancer group and high complement activation animals. Another example is that malnourished mice are strains with mutant genes (dy/dy).
3. Conditions for becoming a variety or strain
As a variety or strain, the following conditions must be met:
1. Similar appearance characteristics, for example, C57BL/6 strain black, DBA/2 mouse shell color strain, coat color, KM strain, coat color is gray and white. Of course, similar appearance characteristics are just one of the conditions that strains and varieties should have. Animals of different strains and varieties have similar appearances. For example, more than a dozen varieties and strains (such as A and KM) have white shells, but other characteristics are also different.
2. Intrinsic biological characteristics The intrinsic biological characteristics are the basis for the existence of strains and varieties. In the course of long-term research, scientists have discovered the biological characteristics of certain animals that are different from other animals, and can maintain these characteristics and guide them to many strains and breeds today. Selected. There are dozens of species of albino mice, but the biological characteristics of each strain and species are more or less different. For example, strain A has a high incidence of breast cancer in postpartum mice, is sensitive to carcinogens, and is prone to lung cancer. Older mice usually suffer from kidney disease. The AKR strain is a spontaneous lymphocytic leukemia; the ICR strain has strong fertility.
3. As a stable genetic performance strain, it should not only have similar appearance characteristics and unique biological characteristics, but more importantly, have stable genetic performance.. Its characteristics have been steadily passed on to the next generation. In other words, strains or varieties require specific breeding values.
4. Strains or variants with a common genetic source and specific genetic structure can be traced back to a common ancestor, branches must be selected and reproduced, and their genetic structure must also be unique. Have. For example, KM mice have a monotype at the Glo-1 locus, NIH mice have a polymorphic distribution of genes, and the frequencies of a and b genes are 67% and 33%, respectively. If the genetic maps of the above two varieties have been established, they have been found to have differences in their genetic maps, and these differences are limited within the variety.
