动物实验,脊椎动物 z-bo 2020-08-31 415

　　A study conducted by Dr. Martinuth and Dr. Andrew Johnson, experts in genetics and cell development in the Department of Life Sciences funded by the Martin Medical Research Council (MRC), showed that the genetic evolution of species, including germplasm, is proven to be rapid. As a result, they tested a new theory that early developmental events can significantly change the body structure and evolution of vertebrates.

　　The original theory was put forward by Dr. Johnson 10 years ago. His view is that the relationship between the germ line (that is, the hereditary germ cells that produce sperm and eggs) and somatic cells (the cells that make up an organism) also affects species diversity. He believes that as species evolve a substance called germplasm, germ cells will become unique, thereby limiting the development of somatic cells and enhancing the ability of species to evolve. Therefore, it is worth noting that vertebrates such as frogs, fruit flies and birds do not look like their ancestors, but they evolve faster than their ancestors.

　　A new look welcomes embryology

　　In the early stages of animal development, embryonic daughter cells are dedicated to producing primordial germ cells (PGC). Primordial germ cells develop into sperm and eggs. The remaining cells develop into somatic cells. Somatic cells are used to represent all the body tissues that make up a person. The germ line is an immortal cell line, passed from generation to generation, and only controls the fertilized egg to form a new embryo. On the other hand, somatic cells die from generation to generation. The most classical biological significance is to explain the influence of natural selection on determining genetic compatibility, leading to the so-called "survival of the fittest". There are two known ways to create

　　PGC. One is the evolutionary preforming theory. A substance called egg cell germplasm is transmitted directly to certain cells of the embryo, and germplasm regulates these cells to become PGCs. Another way is that PGC does not depend on germplasm development. In this case, the secretion signal from a part of the somatic cell induces the formation of PGC, which is called progressive. Dr. Johnson said: "Biologists are used to thinking about how adult somatic cells affect natural selection and the formation of new species. It is not yet clear about the mechanisms of evolutionary embryology and the role of promoting species diversity.

　　A new computer program can test the hypothesis recently published by Dr. Ruth. "We observed as many sequences as possible to study their impact on the changes in germplasm sequences. We analyzed and processed approximately 12 million sequences from 165 species, including mammals and reptiles."

　　Dr. Lusi and graduate student Terry Evans wrote a computer program to process sequences and test hypotheses. They use epigenetics to compare the DNA sequences of species containing genetic resources with their relatives. So, for example, we compared the DNA of amphibian sal (epigene) and frog (germplasm). Unexpectedly, they found that the sequence of species with germplasm changes faster than species without germplasm. Therefore, frogs evolve faster than sal. The same pattern was found in similar comparisons between fish and reptiles. This shows that it is a universal feature of animal evolution. These results support the selective advantage of germplasm because it can evolve faster. In addition, they also support the view that germ line development and somatic cell relationships in the animal kingdom affect the formation of species diversity.

　　Dr. Johnson said: "Martin and I have been looking for a theory that is different from what we expected. This study shows that animals with germplasm may evolve faster. Evolution is usually seen as a gradual process. However, in this In research, it shows that germplasm evolution can lead to explosive radiation of species. It is important that the inheritance between species is accelerated due to the acceleration of evolution. The similarity coefficient may be different from the expected genetic relationship, and genetic relationship has broad biological significance. "

　　But the evolution of germplasm comes at a price.

　　The first thing to note is that animal embryos that contain germplasm are different from embryos that use epigenetics. In fact, the structure of these adults is "typical. Vertebrates." This is why we use sal as an experimental model. am is a "typical vertebrate" and has no germplasm. We have discovered a mechanism that can control the development of the in mammalian embryos. However, this is not seen in "normal" vertebrate development. Therefore, the evolution of germplasm leads to a dead end in evolution. In other words, sal amphibians can evolve into reptiles and then into mammals. Frogs can only evolve into other frogs. There are many types of frogs, but only frogs. Therefore, researchers believe that sal can be used as a model for future human development research.