Those three experiments confirmed that the gene was DNA, not protein?

A brief history of genes (2011-08-2717:14: 59) is reproduced.

Tags: Mendel, American genetic code, random talk on genetic classification: learn and pick it up.

This paper discusses the origin of the word gene and the process of people's exploration and understanding of genes, and points out that a genetics is the history of discovering and studying genes.

Keywords: genetic information; Gene; Deoxyribonucleic acid

China Library Classification Number: Q343. 1 ID number: a.

Gene is a special term in genetics. It can be said that a history of genetics is a history of searching, exploring, studying and understanding genes. Genetics is the study of biological genetic variation. Biological reproduction, offspring similar to parents or ancestors, this "anthropoid" phenomenon is inheritance. But offspring and parents are not completely similar, and even more different, which is variation. Heredity and variation are inseparable, forming a pair of contradictory two aspects, which are both opposite and unified. Heredity ensures the stability of organisms, and variation ensures the evolution of organisms. In this process, choice plays a very important role.

We say that living things have to reproduce to be endless, so what is the bridge between parents and offspring? That is reproduction, that is, cells.

Split. The reproduction of single-celled organisms is achieved by direct division of cells. But the reproduction of multicellular organisms, especially higher organisms, is more complicated: the body.

Cell proliferation depends on somatic cell division; The proliferation of individuals depends on the division of sexual cells and the fusion of male and female cells, that is, fertilization. From the point of view of * * * *, regardless of single-celled organisms or multicellular organisms, what does a parent individual (cell) pass on to its offspring? It is the "genetic information" of the mother cell or individual.

From the ancient Greek and Roman times in the west, even earlier in the East, people have been constantly looking for and exploring reproductive and genetic phenomena, that is, in

Looking for "genetic information". On the basis of atomism, Hippocrates, Anaxagoras and democritus put forward the theory of the birth of the universe, Aristotle put forward the theory of blood, Alkell Marron's theory of sex determination, parmenides and others' theory of left and right, all of which are groundbreaking works to explore reproduction and heredity. Of course, almost none of their theories are correct, but they have great influence on later generations.

Lamarck, Darwin, weismann, Spencer, Dewey and others. These people, such as the universal son put forward by Darwin, the determinant or germplasm put forward by weismann, the universal son put forward by Dwellis and the physiological unit put forward by Spencer, can all be regarded as speculative forms of genetic particles or genetic genes.

18 ~ 19 century, due to the development of animal-plant hybridization and the progress of microscope and cytology research, the door to reveal the genetic law and genetic material basis was opened. From 65438 to 0865, the Austrian monk Grigo Mendel published his paper "Experiment of Plant Hybridization" on the basis of pea experiment for eight consecutive years, and put forward two laws of genetics-separation phenomenon and law of free combination. After being buried for 35 years, these two laws were rediscovered by three European botanists Collins, Defrees and Cermak in 1900, and widely publicized by batson and others in Britain, so they were born.

Real scientific genetics was born, and 1900 is recognized as the age when modern genetics was born. The essence of Mendel's law is to announce to the world that heredity is "granular", and it is this granular thing that parents pass on to their offspring, which he calls "genetic factor". Later, Danish geneticist John

Johnson changed his name to "gene", so the word "gene" was quickly recognized as a concept or symbol to express biological genetic variation.

However, what exactly is a gene? Where is it? Scientists have been exploring for a long time. Published by Wilson in the United States at the beginning of this century.

The book Principles of Development and Genetics made a comprehensive summary of cytological knowledge at that time. He clearly pointed out that genetic material is in the nucleus, but it is

A polymer compound. 1903, Sutton, a young American graduate student, pointed out that the behavior of Mendel's genetic factors is parallel to that of chromosomes in cell division, so he and Boveri proposed that genes are on chromosomes almost at the same time.

Thomas morgan, an embryologist and geneticist from Columbia University in the United States, and a group of his students started a hybrid experiment on Drosophila from 19 10, which confirmed Mendel's laws of separation and free combination in pea experiments, and also found the laws of sex-linked inheritance and gene chain exchange. And he pointed out that genetic genes do exist on chromosomes, and they are arranged in a straight line with a certain distance and order from each other.

Morgan published his masterpiece Gene Theory in 1927. He and his students drew the genetic map of Drosophila. Almost at the same time, Emerson, mcclintock and others studied maize and drew the linkage genetic map of maize genes, thus making progress in Mendel genetics.

Enter a new era of cytogenetics.

Furthermore, people have to ask, what kind of substance is a gene? That is, what are its chemical properties? Many scientists have made explorations. 194 1

In 1996, American geneticists Bedell and Tatem thought that genes were related to enzymes and put forward the theory of "one gene, one enzyme". In 1944, Wei Rui and others concluded that the transforming factor is a substance called deoxyribonucleic acid, or DNA for short. place

Transformation is the transformation of biological genetic characteristics, and this transformation factor can only be DNA, not protein. For a long time, people thought that "genes are eggs"

Corrected the wrong concept of "white matter". 1946, lederberg and Hess found that different bacteria can also hybridize, and bacteria

Similarly, the hybrid recombination of bacteria is also the result of DNA exchange of genetic material. 1952 Hershey and Chase infected Escherichia coli with the most primitive organism-phage. The infection test shows that only DNA can enter E.coli and form new progeny phage, but protein has no such effect. At the same time, American geneticist Benzer infected bacterial cells with different phages. The experimental results show that phage DNA can also be hybridized and recombined, which proves that the gene is a functional unit and can be subdivided inside the gene. A functional unit is called a "cistron", and a cistron is equivalent to a "gene". Cistrans contains many recombinants and mutants. Benze's cistron theory revised Morgan's understanding of genes. They believe that gene is not only a functional unit, but also a mutant unit and a recombinant unit, that is, the concept of "trinity".

By the early 1950s, the chemical properties of genetic material DNA had been well understood. Of course, the study of nucleic acid chemistry has a history of more than 80 years, if it started with the separation of nuclear protein by Michelle in 1866. By the early 1950s, it was known that DNA was composed of deoxyribose, phosphoric acid and four bases (adenine A, thymine T, guanine G and cytosine C). Each base forms a nucleotide with a deoxyribose and a phosphoric acid. In other words, DNA macromolecules are composed of four kinds of single nucleotides. Moreover, we know that in DNA molecules, adenine nucleotide is always equal to thymine nucleotide and guanine nucleotide is always equal to cytosine nucleotide, that is, A = T and G = C. All these knowledge and progress are brewing a great discovery: this is the spatial structure of DNA molecules.

1953, Watson (1928-), an American graduate student and molecular geneticist, and Crick (19 16-), a British biochemist, won two Nobel Prizes for their research on the diffraction of DNA molecules by British crystallographers Wilkinson, Franklin and Chen Drew.

American biochemist Pauling, the winner of this prize, was inspired by protein's structural research and successfully put forward the spatial structure model of DNA double helix. This structural model solves many problems such as self-replication of DNA molecules and transmission of genetic information (transcription and translation). It is called the greatest discovery and the second important milestone in the history of biology since Darwin put forward the theory of evolution. The two of them published this achievement in the British magazine Nature. The paper with less than 2000 words was so shocking that they won the Nobel Prize in Physiology and Medicine with Wilkinson as 1962.

In the early 1960s, based on the discovery of the spatial structure of DNA double helix, two important discoveries were made. One is French scientists Jacob and Mono.

On the establishment of gene regulation theory: one is the decoding of genetic code by American scientist nirenberg and others. Jacob and Mono's gene regulation theory is mainly obtained from the study of lactose metabolism in Escherichia coli. It shows that the three structural genes related to lactose metabolism are regulated by the other three genes. Just like several light bulbs connected in series or in parallel are affected by several power switches. This is of great significance for studying the interaction between genes and truly understanding the action pathway of genes, especially for genetic engineering. Almost every character of living things is related to protein. How does DNA determine the formation of protein? How is the genetic information contained in DNA transferred to protein? These are some rather complicated problems. Deciphering the genetic code in DNA (gene) is a key problem.

The concept of "genetic code" was first put forward by Austrian physicist Schrodinger. He wrote a book called "What is life?" In the early 1940s. In this book, he expressed the idea of genetic code. It is said that his idea of generating genetic code is very poetic. In the process of introducing quantum mechanics theory into the field of biology, he found a way to explore in his philosophical and romantic imagination. He imagined himself sitting on a wooded hillside and the sun was setting. Throughout the ages, the world has experienced many vicissitudes. Maybe a hundred years ago, another man was sitting here, staring at the sunset of the glacier. This person is also born to his parents and has the same pains and joys. So, why do you happen to be you, not him? Maybe, you and he are actually the same. The life you are living now is just a bud on the ancient sacred tree of life. The birth of an individual does not mean that I was created for the first time, nor does my death mean the end of the essence of life. It is this series of imagination that prompted Schrodinger to put forward the concept of genetic code of life and put forward that "every such organism is the blueprint of the next organism", thus laying the foundation for the birth of molecular biology and molecular genetics.

So, what is the genetic code? 1955, the former Soviet Union-American physicist Gamov proposed that three nucleotides in a DNA molecule determine an amino acid in protein. Because there are four kinds of nucleotides in DNA molecule, if an amino acid is determined by three kinds of nucleotides, then the cube of four = 64 permutations is enough to encode 20 kinds of amino acids in protein. His idea of 196 1 year was confirmed by Crick's genetic experiment on E.coli T 4 phage. In the same year, American biochemist nirenberg and others tried to decipher the genetic code, and finally found out all the genetic codes in 1966. This is mankind's understanding of the nature of living things and their own lives. People are different from other animals and plants because of their different genetic codes. However, because people are human beings, they are also creatures, and there are many similarities in genetic code: all creatures use the same genetic code table.

Now we can give a definition of "gene" and make a general summary: gene contains specific genetic information in biological DNA molecules.

Nucleotide sequence is the smallest functional unit of genetic material, and a gene is roughly composed of 1 000 nucleotide pairs.

To sum up, with the development of science, people's understanding of genes is deepening. From the initial understanding of genetic factors to the chemical properties of genes

The understanding of nature promotes genetics from the earliest classical genetics, through cytogenetics, biochemical genetics and finally to molecular genetics.

Duan.

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Genetic information carrier-gene

Ren Benming, Wang Hong

(Biology Department of Xi 'an Xu University, 7 1006 1, China)