The characteristics and application significance of inbred lines and closed herds were compared

Mainly, inbred lines are inbred with a degree of more than 20 generations; And the closed group of animals only needs 4 generations I have painstakingly sorted out the content carefully Look carefully: inbred line: genetic homozygosity, all animals in an inbred line should be homozygous for the gene loci, and the offspring of any individual mating in this strain should also be homozygous, that is, the genotype is the same, and the genetic characteristics are the same.

Theoretically, these animals should not have hidden recessive genes.

When experiments are done with inbred animals, the consistency of experimental results will not be affected by the exposure of recessive genes. Consistency of phenotype, due to the above characteristics, any heritable signs of inbred animals should be consistent, such as physiological, biochemical, histological, morphological characteristics (coat color, weight, etc.), and even the type of behavior tends to be consistent. If there are sometimes some differences between individuals, it can only be caused by the different acquired circumstances.

Genetic stability and responsiveness, inbred lines are bred by inbreeding for more than 20 generations, and the heritability is stable. Once an inbred line has been identified, the probability of genetic variation is very low as long as inbreeding is insisted on and constantly monitored. Since the heredity of inbred animals is highly homozygous, the response is highly sensitive to the influence of various external factors, including test factors.

This type of animal is like a high degree of precision.

The balance will swing with a slight change in the outside world. The discriminability of genetic traits, in the same inbred line, there should be no genetic polymorphism. In the vast majority of inbred lines, the main genetic loci have been typed, and the animal strain can be identified through genetic testing, which is conducive to the maintenance of genetic homozygosity of the strain.

Significance: Because the inbred line has good genetic characteristics suitable for experimental requirements, it is used in many experimental fields, and the amount of animals used in each batch of experiments can be reduced, and it is easy to obtain statistically significant experimental data. They are ideal materials for embryology, physiology, and genetics research, and are also used for efficacy testing and safety evaluation.

and other animal experiments. Inbred lines are indispensable for tissue or tumor transplantation experiments and for the creation of animal models of certain genetic human diseases. Closed group animalsClosed group animals have a certain degree of heterozygosity in genetivity, so this kind of animals has high fecundity, strong adaptability, low cost of seed preservation and reproduction production, and a wide range of applications.

Compared with inbred lines, individuals in closed groups are still genetically quite different, so the reproducibility of experiments and the consistency of responses are not as good as those of inbred lines. However, in the experiments, the closed group animals have characteristics that are closer to the natural population response than the inbred lines. Therefore, in practice, closed group animals are widely used in teaching, pre-experiments, general drug screening, and toxicity and safety evaluation tests.

Inbred animals: Inbred lines refer to animals with a degree of inbreeding equivalent to more than 20 generations of continuous whole sibling or parent-child mating, with an inbreeding coefficient of more than 10 generations, and a high degree of homozygous and stable population genes.

Inbred lines: Obtained by mating all siblings for 20 or more generations, all animal individuals can be traced back to a pair of common ancestors in their 20s and beyond, and the inbreeding coefficient is above and above, with an average increase of 16% per generation. It can be considered that the individuals in the inbred line have the same genotype, so their adaptability to changes in the external environment is poor. In addition, its reproductive ability, longevity, growth rate, susceptibility to disease, physical strength and vitality are all affected.

Closed group: In the case of non-inbreeding mating, mating for 4 or more generations in a row is formed, and the differences between individuals in the closed group depend on the genetic composition of their parents, and the inbreeding coefficient of each generation increases by less than 1%. The closed group of animals has a large gene pool and high heterozygosity of genes, so they have strong adaptability to environmental changes, and are more sensitive to reproductive ability, longevity, growth rate, disease susceptibility, physical strength and vitality.

Inbred animals are prone to birth defects (the onset of recessive gene homozygosity due to increased homozygosity) but not necessarily defective, just as the incidence of genetic diseases of human inbreeding is significantly increased, but not everyone. Those who are sick can be eliminated when doing inbreeding. For example, rats and rats have albinism, but they are not yet affected.

Correct Answer: a

Analysis: Inbred animals are generally called pure pitian animals, which refer to pure early grip strains that have been bred by brother and sister for more than 20 generations.

Inbred animals: Strains bred by sibling mating (BS) or parent-child mating (PO) for more than 20 generations. Rodents such as mice and rats are selected for breeding.

Closed herd: that is, a population of animals is located in a fixed place, does not introduce any new species from outside for more than 5 years, and only mates randomly within the group to reproduce. The animal can be ** inbred or non-inbred lines, can maintain the general characteristics of the group, and is easy to reproduce in large numbers.

At present, the commonly used ones are Kunming mice, Wistar rats, blue rabbits, etc.

One lives in a group, the other lives alone.

One lives in a group and the other lives alone.

Consciously select male and female individuals who are relatively close in blood from an animal group, that is, brothers and sisters, mothers and sons, fathers and daughters with common ancestors, for mating, this kind of inbreeding is called inbring; Animals that have been bred by mating between all siblings or between parents and offspring for at least 20 consecutive generations are called inbred strain; Also known as pure animals. Such as BALB C mice, C57BL 6J mice, etc. All individuals within the inbred line can be traced back to a pair of common ancestors that originated in the 20th or later generations.