2 English reference clone
Note "clone" is a transliteration of English clone, which refers to the offspring individual population with the same genotype formed by cell asexual reproduction, referred to as "asexual reproduction".
Cloning technology was introduced into horticulture in 1903, and then gradually applied to botany, zoology and medicine. We often encounter "cloning" in a broad sense in our daily life, but it is not called "cloning".
In spring, people cut off the branches of plants and insert them into the soil, which will soon germinate and grow new plants. These plants are plants with exactly the same genetic material composition. This is called "cloning". Also, the tubers of plants such as potatoes are cut into many small pieces for reproduction, and the offspring produced are also "clones". These are all asexual reproduction of plants, or "cloning". This phenomenon is so common that almost everyone has seen it.
There is also asexual reproduction in the animal kingdom, but it is more common in invertebrates, such as split reproduction of protozoa and budding reproduction of caudate animals. But for advanced animals, under natural conditions, they can only reproduce sexually, so scientists must go through a series of complicated operating procedures to make them reproduce asexually. In 1950s, scientists successfully cloned an amphibian? Xenopus laevis opens a new chapter in cell biology.
In the late 1980s, Britain and China successively used embryonic cells as donors to "clone" mammals. By the mid-1990s, China had cloned five kinds of mammals, including mice, rabbits, goats, cows and pigs.
1On February 23rd, 997, scientists from the Roslin Institute in Scotland announced that their research team had successfully "cloned" Dolly, a lamb with the same genetic structure as the donor, and the world public opinion was in an uproar. What is special about Dolly is that it was born without the participation of * * *. The researchers first sucked genetic material from a sheep's egg cell and turned it into an empty shell, then took out breast cells from a 6-year-old ewe and injected genetic material into the empty shell of the egg cell. In this way, an egg cell containing new genetic material but not refined was obtained. This modified egg cell divides and proliferates to form an embryo, which is then implanted into the uterus of another ewe. With the smooth delivery of ewes, "Dolly" came into this world.
But why don't other cloned animals have such great influence in the world? This is because the genetic genes of other cloned animals come from embryos, and they are all nuclear transplants with embryonic cells, which cannot be strictly said to be "asexual reproduction". Another reason is that the embryonic cell itself is sexually propagated, and the genome in its nucleus is half from the father and half from the mother. Dolly's genome comes from a single parent and is truly asexual. Therefore, strictly speaking, "Dolly" is the first truly cloned mammal in the world. It is characterized by its relationship with the donors who provide it with genetic material? The 6-year-old ewe has exactly the same gene and is a copy of the ewe.
The birth of "Dolly" means that human beings can produce the same life in large quantities from the tissues and cells of an animal just like copying tapes or files, which is undoubtedly a breakthrough in the field of genetic engineering research.
Cloning technology is the result of scientific development and has a very broad application prospect. In horticulture and animal husbandry, cloning technology is an ideal means to cultivate varieties with stable genetic traits. Through cloning technology, high-quality fruit trees and improved livestock can be cultivated. In the medical field, the United States, Switzerland and other countries have been able to use "cloning" technology to cultivate human skin for skin grafting. This new achievement avoids the possible rejection of skin allograft and brings good news to patients. According to China Xinhua News Agency1April 4, 1997, Cao Yilin, an expert in plastic surgery in Shanghai Ninth People's Hospital, successfully cloned human ears in mice for the first time in the world, which brought hope for the repair and reconstruction of missing organs in human body. Cloning technology can also be used to breed many valuable genes, such as insulin for treating diabetes, growth hormone that is expected to make patients with Zhu Ru disease grow taller again, and interferon that can resist many diseases and infections.