Morgan Jr. was born a "naturalist" and was curious about everything in nature. His favorite games are catching butterflies, insects, digging nests and collecting grotesque and colorful stones in the wild. He often stays on the ground for a long time and carefully observes how insects feed and nest. Sometimes he will take the captured insects and birds home to dissect and see the internal structure of their bodies.
When little Morgan/Kloc-0 was 0/0 years old, at his repeated request, his parents agreed to give him two rooms at home for his exclusive use. So, he began to paint and paste wallpaper, redecorated two rooms according to his own wishes, and then filled them with various specimens of birds, eggs, butterflies, fossils, minerals and so on collected and made by himself. Until Morgan died, the furnishings in these two rooms were still the same as when he was a teenager.
Another hobby of Morgan Jr. is reading, especially books about nature and biology. If no one invites him to dinner, he can soak in the study all day. Morgan also has a habit that he has developed since he was a child, that is, he is sloppy. He never asks his parents to buy new clothes, and he is not embarrassed by the shabby clothes. Morgan's love of knowledge made him pour great enthusiasm into learning. A few days after 14' s birthday, he graduated from junior high school and was admitted to Kentucky State College. The pre-university courses in the United States are actually equivalent to the high schools in some high schools affiliated to universities in China. Two years later, 16-year-old Morgan successfully transferred to the undergraduate course. He chose science as his major and studied mathematics, physics, chemistry, astronomy, natural history, agriculture and applied engineering. Natural history, which he was most interested in, ran through the four-year college curriculum, and he was fortunate to meet two outstanding natural history professors. Morgan's interest in natural history continued until his later years, and later he engaged in embryology and genetics research, which can be said to be the natural development and deepening of his interest in natural history since childhood.
When I graduated from Morgan University, I didn't think about my future development direction. After graduation, some students went to the sea to do business, some taught, some ran farms, and some went to the geological team, but Morgan was not interested in these jobs. In his own words: I decided to go to graduate school because I didn't know what to do. He applied to the biology department of the graduate school of Hopkins University. At that time, Hopkins University was founded only 10 years ago, with a small scale and little reputation. He made this choice mainly because Hopkins University is located in Maryland, his mother's hometown, and biology is a major closely related to natural history.
Hopkins University is good at medicine and biology, and its educational direction is mainly postgraduate education. In particular, we attach great importance to basic research and cultivate students' hands-on experimental ability. Different from other universities in the United States at that time, the teaching purpose of biology major in this university is not mainly for the application in medicine and agricultural production, but mainly for basic scientific research, and almost all courses are conducted in the laboratory, and pure classroom teaching is actually cancelled. The school also attaches great importance to cultivating students' rigorous and realistic scientific spirit and serious work attitude through experiments. Professor Martin, then head of the Department of Biology, once warned students: "Don't think that the equipment in the laboratory is an automatic' physiological enema machine'-from this stuffed animal, pull a wrench and an important scientific discovery will come out at the other end." Hopkins University is ahead of other American universities in teaching concepts and teaching methods, which is one of the reasons why it has successfully trained seven Nobel Prize winners in Physiology and Medicine and become a world-famous university.
The unique teaching method of Hopkins University laid a good foundation for Morgan's future research, and made him form the creed of "everything must pass the test". He believes that the experimental results are better than the conclusions of authoritative organizations. He used to be skeptical about Darwin's theory of evolution and Mendel's theory of heredity, but the experimental results finally convinced him of the above theory and made it develop and perfect. Almost all his important research results were obtained from experiments. Two years later, Morgan received a master's degree, and his alma mater, Kentucky State College, sent him a letter of appointment, appointing him as a professor of natural history. Although his father didn't have a fixed job at that time and his family was embarrassed, as the eldest son, he urgently needed to shoulder the burden of family economy. But at this time, Morgan has firmly established his ideal of engaging in basic research in biology, and he stayed at Hopkins University to continue his doctoral studies. During his doctoral studies and for more than 10 years after receiving his doctorate, Morgan mainly engaged in experimental embryology research. 1900, Mendel died 16 years later, his genetic theory was rediscovered. Morgan also gradually turned his research direction to the field of genetics. Morgan believed in these laws at first because they were based on conclusive experiments. But later, many questions made Morgan more and more doubt Mendel's theory. He used a white-bellied yellow-sided house mouse to cross with the wild type, and the results were varied. But at the same time, Defrees's mutation theory made him more and more satisfied, and he began to experiment with fruit flies to induce mutation. His laboratory was nicknamed "the fly room" by his colleagues. Besides some old tables, there are thousands of milk cans in Qian Qian, which have cultivated thousands of fruit flies. 19 10 In May, his wife and laboratory technicians found a strange male fly, whose eyes were not red like his brothers and sisters, but white. This is obviously a mutant, destined to become the most famous insect in the history of science. At this time, the Morgan family had just added a third child. When he went to the hospital to see his wife, the first sentence was "What happened to that white-eyed fruit fly?" His third child is fine, but the white-eyed male fruit fly is weak. Morgan cherished this fruit fly very much, put it in a bottle, put it beside him when he slept, and brought it back to the laboratory during the day. In this way, it preserved its strength, and finally died after mating with a normal red-eyed female fly, leaving a mutant gene and later multiplying into a large family.
The descendants of this family are all red-eyed. Obviously, red and white are dominant, which coincides with Mendel's experimental results. Morgan was secretly surprised. He mated his offspring again and found that the ratio of the second generation of red and white fruit flies was exactly 3: 1, which was also the result of Mendel's research, so Morgan worshipped Mendel more.
Morgan is determined to follow this clue and see how animals are inherited. He further observed that the second generation of white-eyed fruit flies are all males, which shows that the sex (male) factors of the trait (white) are linked together, and during cell division, the chromosome first changes from one to two, which shows that it can inherit the trait, and the sex gene is on the chromosome and passed down from generation to generation through cell division.
Chromosome is the carrier of gene! Morgan and his students also calculated the chromosome positions of various genes, and mapped the positions of genes arranged on four pairs of chromosomes in Drosophila. Since then, the genetic theory was born, and the mystery of male and female sex was finally revealed. Since then, genetics has ended the utopian era, and major discoveries have followed, becoming the most active research field in the 20th century. For this, Morgan won the 1933 Nobel Prize in Physiology and Medicine. He is the first winner of the Nobel Prize in Physiology and Medicine in Hopkins University and the United States. He is also the second scientist to win the Nobel Prize for his achievements in genetic research. During his years of studying and teaching at Hopkins University, Morgan has been paying close attention to the progress of biology. 1900 When Mendel's genetic research was rediscovered, new news of genetics reached Morgan's ears. Morgan initially expressed doubts about Mendel theory and chromosome theory. He raised a very sharp question: the sex of an organism must be controlled by genes. So, is the sex-determining gene dominant or recessive? No matter how you answer, you will face an out-of-control situation. In nature, the sex ratio of most organisms is 1: 1. No matter whether the sex gene is dominant or recessive, such a ratio will not be obtained. In order to verify Mendel's law, Morgan did the experiment himself. He crossed the house mouse with the wild mouse and got all kinds of results, which could not be explained by law at all. Moreover, the idea that there are genes on chromosomes was only speculation at that time. Explaining Mendel's genetic theory with conjectural theory, Morgan, who insists on the principle of "everything passes experiment", thinks it is not credible. Doubt to doubt, Morgan is still busy in his laboratory. From 65438 to 0908, he began to use fruit flies as experimental materials to study the mutation of biological genetic traits. Drosophila belongs to the category of flies, but it is smaller than the flies we see every day, with a body length of only half a centimeter. A bottle can hold hundreds. Drosophila likes to eat rotten fruits, so people can see them in front of fruit stalls in summer, hence the name. As experimental materials, fruit flies are easy to raise, and a little banana pulp can make them full all day; Drosophila is very fertile. Eggs can hatch into maggots in 1 day, pupate in 2 to 3 days, emerge into adults in 5 days, and can reproduce for 30 generations a year. The chromosomes in Drosophila cells are very simple, with only 4 pairs of 8 chromosomes, which are clearly distinguishable. The rapid propagation of fruit flies has caused a strange phenomenon to the residents near the laboratory. The milk bottles they put in front of their homes are often lost. Where are so many bottles? It turns out that in order to hold a large number of fruit flies, Morgan and his graduate students sometimes act as "gentlemen on the beam" and steal milk bottles from nearby residents.
The first fruit flies were "confined" by Morgan. He asked one of his graduate students to raise fruit flies in a dark environment, hoping that there would be varieties whose eyesight would gradually disappear or even their eyes would shrink or shift because they were not used for a long time. Although it has been bred for 69 generations in a row, the fruit fly that has never seen the light of day still stares. When the 69th generation fruit flies first appeared, they couldn't keep their eyes open for a while. The graduate student excitedly asked Morgan to come and have a look. Before the two of them could clap their hands and cheer for the success of the experiment, the fruit fly returned to its normal state and swaggered to the window, leaving two stunned teachers and students. Morgan has done such disastrous experiments many times. He often carries out dozens of experiments at the same time. As expected, many experiments came to a dead end. Sometimes Morgan laughs at himself and says that his experiments can be divided into three categories: the first category is stupid experiments, the second category is stupid experiments, and another category is more stupid than the second category. Despite repeated defeats and wars, Morgan suffered repeated defeats and wars, because he knew that in scientific research, as long as there was a meaningful experiment, all the labor paid would be rewarded.
Sure enough, another experiment about fruit flies finally caused a sensation all over the world. These fruit flies were "tortured" by Morgan. They were irradiated with X-rays and lasers, and sugar, salt, acid and alkali were added at different temperatures, and even the fruit flies were not allowed to sleep. Mutations have been induced in Drosophila by various methods. Two years passed quickly. In 19 10, a friend of Morgan came to visit him. Facing the rows of fruit fly experimental bottles in the laboratory, Morgan sighed slightly sadly: "Two years' efforts were in vain. I have been feeding fruit flies for the past two years, but I have got nothing. " Sometimes hope is always born in despair. 19 10 In May, Mrs. Morgan found an abnormal white-eyed male fruit fly among red-eyed fruit flies. He has never seen such a type, so this fruit fly is a rare mutant.
Morgan was very excited. He put this precious fruit fly in a separate bottle. Every night, Morgan takes the fruit fly home, puts the experimental bottle beside him when he sleeps, and takes it to work during the day for fear of accidents. Under his careful care, the weak white-eyed Drosophila finally died after mating with a red-eyed female Drosophila, leaving the mutated gene to the next generation of Drosophila and Morgan, who painstakingly cultivated it. Ten days later, the first generation of hybrid fruit flies grew up, all red-eyed fruit flies. Don't worry, there is no white eye gene. According to Mendel's theory, the red-eye gene is dominant relative to the white-eye gene, so the precious mutant gene is just hidden in the background. Of course, Morgan will not miss the opportunity to test the previous theory. He used the first generation of hybrid fruit flies to mate with each other and produced the second generation of hybrid fruit flies. After waiting anxiously for more than ten days, Morgan got the second generation of hybrid fruit flies, including 3470 red eyes and 782 white eyes, with a basic matching ratio of 3: 1. This time, Morgan really believed in Mendel, and the experimental results were completely in line with the law that Mendel summed up from peas. When Morgan sat next to the microscope and observed these staring fruit flies again, he found a phenomenon different from Mendel's law. According to Mendel's law of free combination, those white-eyed fruit flies should be male and female. However, these white-eyed fruit flies are all males, and none of them are females. In other words, the mutant white-eyed gene is inherited by male individuals. Morgan finally saw something from fruit flies that Mendel couldn't observe on peas. The explanation of special phenomena is to establish new laws. Morgan knows that one of the four pairs of chromosomes in fruit flies is decisive. Among them, the two sex chromosomes in female Drosophila are exactly the same, and they are recorded as XX chromosomes. The sex chromosomes of male Drosophila melanogaster are one big and one small, which are recorded as XY chromosomes. Morgan judged that the white eye gene was located on the X chromosome.
So when his little white-eyed Drosophila mates with a normal red-eyed Drosophila, because red eye is the dominant gene, the offspring are red-eyed Drosophila regardless of sex; In the second hybridization, the female Drosophila melanogaster with supercilious look gene will mate with the normal male Drosophila melanogaster, and an X chromosome with supercilious look gene will combine with a Y chromosome, resulting in supercilious look in the second generation of hybrid Drosophila melanogaster, all of which are males. Morgan called this phenomenon that the white-eyed gene follows the inheritance of X chromosome "linkage". The two genes-the white-eyed gene and the sex-determining gene-are hinged together like a chain, and they work together when the chromosome pairs in the cell divide and combine with other chromosomes.
It took Morgan and his students two years to find the mutant white-eyed fruit fly. After the discovery of the first mutant fruit fly, other mutant types followed. A few months later, they found four blink mutations. For example, fruit flies have red eyes. The separation and combination of this shape has nothing to do with gender and supercilious genes. Obviously, the red-eye gene is located on another chromosome, not on the sex chromosome. The genetic characteristics of Drosophila cinnabarina are completely consistent with Drosophila melanogaster, and they are also sex linked, indicating that both genes are located on the X chromosome.
Morgan's students discovered a mutant trait-the winglet gene of fruit fly, which challenged Morgan's new theory. This mutant gene is sex-linked and located on the X chromosome like the white eye gene. However, when chromosomes are paired, the two genes sometimes don't seem to be connected. For example, according to the linkage principle, the next generation of white-eyed small-winged fruit flies should have only two types, either white-eyed small wings or red-eyed normal wings. However, Morgan found that there are also some types of wings with normal white eyes and small red eyes. Need to explain the phenomenon again. Morgan pointed out that gene linkage groups on chromosomes are not as strong as chains, and sometimes chromosomes break and even exchange some genes with another chromosome. The farther the two genes are located on chromosomes, the greater the possibility of changes between them and the greater the frequency of gene exchange between chromosomes. Although the white-eyed gene and winglet gene are on the same chromosome, they are far apart, so when some genes are exchanged between chromosomes, new types will appear in the offspring of Drosophila. This is the law of "exchange".
The law of chain exchange is Morgan's great contribution in the field of genetics. Together with Mendel's separation phenomenon and the law of free combination, it is called the three laws of genetics. Although Morgan hates empty talk and pays attention to experiments, the paper that won him the most reputation is not a description of experiments, but a theoretical article on the law of chain exchange published in Science magazine, without any experimental data.
1one afternoon in 933, Morgan was sitting in his yard reading a novel that was popular in that year, and he enjoyed it very much. At this time, the family received a telegram saying that on the occasion of the centenary of Nobel's birth, "Morgan was awarded the Nobel Prize for his contribution to the genetic chromosome theory". Morgan didn't go to Sweden to attend the award ceremony on the pretext that he was too busy at work. Actually, it's because he doesn't like to appear in public meetings in a serious way. Apart from scientific seminars, he is not interested in politics or other meetings. After receiving the bonus, Morgan insisted on dividing it into three parts, one for himself and one for each student in the two laboratories. In Morgan's view, honor and bonus should belong to everyone.
194 1 year, 75-year-old Morgan announced his retirement and left the laboratory. /kloc-0 died at the end of 945. Perhaps the best memory of him is to call the unit distance between genes in Drosophila chromosome map "Morgan". His name has been passed down as a genetic research unit. 19 10 In May, a male fruit fly with white eyes was born in Morgan's laboratory. Morgan took it home, put it in a bottle by the bed and brought it back to the lab during the day. Soon he mated this fruit fly with another red-eyed female fruit fly. Among the next generation of fruit flies, there are 1240 red-eyed fruit flies. Later, Morgan mated a white-eyed female fruit fly with a normal male fruit fly. But in their offspring, the male fruit flies with half red eyes and half white eyes, while the female fruit flies without white eyes, all females are normal red eyes. How does Morgan explain this phenomenon? He said: "The eye color gene (R) is tied to the sex-determining gene, which is on the X chromosome." Or, as we say now, it is linked. If we get an X chromosome and a Y chromosome with the white-eyed gene, we will develop into a white-eyed male fruit fly.
Morgan, his colleagues and students used fruit flies as experimental materials. By 1925, it has been found that this little creature has four pairs of chromosomes, and about 100 different genes have been identified. And the degree of linkage determined by mating test can be used to measure the distance between genes on chromosomes. 19 1 1 year, he put forward the theory of chromosome inheritance. Drosophila brought such a great success to Morgan's research that some people later said that this fruit fly was specially created by God for Morgan. Morgan found that genes representing biological genetic secrets do exist on the chromosomes of germ cells. In addition, he also found that genes are arranged in a straight line in each chromosome.
Chromosomes can be freely combined, but genes arranged on one chromosome cannot be freely combined. Morgan called this feature "linkage" of genes. In the long-term experiment, Morgan found that genes were exchanged because of the separation and combination of homologous chromosomes. But the exchange is very small, accounting for only 1%. The law of chain exchange is the third genetic law discovered by Morgan. He founded the famous gene theory in the 1920s, revealing that genes are the genetic units that make up chromosomes, which can control the development of genetic traits and are also the basic units of mutation, recombination and exchange. But what exactly are genes made of? This was still a mystery at that time. 1933, Morgan won the Nobel Prize in Physiology and Medicine. Morgan devoted his life to embryology and genetics, and founded the "gene theory" of modern genetics on the basis of Mendel's law. He has studied many kinds of creatures (including many kinds of marine creatures) and biological problems; Using Drosophila to carry out genetic research, it is found that chromosome is the carrier of gene and the law of sex-linked inheritance is established. The phenomena of linkage, exchange and non-separation between genes located on the same chromosome were discovered, and the third law of genetics-the law of linkage exchange was established. More than 400 kinds of mutant genes were located on chromosomes to make chromosome maps, that is, linkage maps of genes. The monograph "The Theory of Genes" was published in 1926, which gave a concrete and clear description of the basic concepts of genetics.
The gene theory he founded realized the first theoretical synthesis in genetics. It has built a genetic bridge between embryology and evolution, promoted the development of cytology, promoted the transition of biological research from cellular level to molecular level, and penetrated genetics into other disciplines of biology, laying the foundation for realizing new comprehensive biology. In addition, he was awarded the Darwin Medal (1924) and the Coppler Medal (1939) by the Royal Society. His works cover several important fields of biology, including evolution and adaptation, experimental embryology, embryology and genetics, and gene theory.