What are human genes?

(a) Genetic "factors" The original concept of genes was derived from Mendel's genetic "factors", which suggested that the inheritance of biological traits was controlled by genetic factors, and that the traits themselves could not be inherited, but rather the genetic factors that controlled them were the ones that were inherited. In 1909, a Danish scholar, W.L Johannsen, proposed that the genetic factor of a trait is hereditary. Danish scholar W. L. Johannsen proposed the term "gene" (gene), instead of Mendel's genetic factors, and thus formed a "particle inheritance" doctrine. That in hybrids, alleles are not fused, and each maintains its independence, which is the core of Mendel's law of inheritance.

(B) chromosomes are carriers of genes In 1910, Morgan and other State fly hybridization experiments show that the behavior of chromosomes in cell division and gene behavior. Thus proving that genes are located on chromosomes and arranged in a straight line, put forward the law of continuous exchange of genetics. It proved that sex determination is governed by chromosomes and published Theory of Genes in 1926. This theory reveals the relationship between genes and traits phase hereditary transmission law, established the chromosome doctrine of heredity, laid an important foundation for cytogenetics. He himself was awarded the Nobel Prize in 1933. Morgan scientifically foresaw that genes are a chemical entity. And that genes control the corresponding traits, genes can be mutated, genes can be exchanged, thus proposing that genes are both a functional unit. It is a mutation unit, but also an exchange unit of the "Trinity" concept.

(C) DNA is the genetic material since Morgan. Several scientists have proved that there is a correspondence between multi-line chromosomes and germ cell chromosomes, put forward multi-line chromosomes on the transverse pattern is the hypothesis of the gene, and experimental confirmation, thus pushing the form of the gene to the entity; Griffith in 1928 first discovered the transformation of pneumococcal bacteria, i.e., high temperature to kill the pathogenicity of the S strain of bacteria, can be changed to become the non-pathogenicity of the R strain of bacteria with The effect of killing the pathogenic S strain of bacteria with high temperature can change the non-pathogenic R strain into a pathogenic one. This phenomenon of changing genetic traits is called bacterial transformation (transformation), the experiment opened the way for the study of determining the chemical nature of the genetic material. 1944 AVery et al. not only succeeded in repeating the above experiments in vitro, but also proved biochemically that the transforming factor (trans-foming factor) is DNA, not polysaccharide pods, proteins and proteins. polysaccharide pods, proteins and RNA, and that the frequency of transformation increased with the purity of DNA. When DNA is degraded by treatment with DNAase (DNase), no transformation occurs, but other enzymes, such as proteases, have no effect on this transforming ability. Also this transformation can be carried out in vitro. This experiment fully demonstrated that it is the transfer of DNA fragments of s-type that converts R-type to S-type, proving that DNA is the genetic material.

(D) genes are functional DNA fragments In the 1940s, G. w. BeadIe and E. L. Tatum, through the study of the nutritional defective type of rough vein spores, put forward the hypothesis of a gene and an enzyme. This hypothesis bridged the study of protein synthesis in biochemistry with the study of gene function in genetics. It also laid the foundation for the decoding of the genetic code and the indication of the process of information transfer between macromolecules in the cell. In particular, in 1953, watson and crick proposed the double helix structure model of DNA, which clarified the way of DNA replication in the living body. 1957 by crick first proposed the basic law of genetic information transfer between biological macromolecules in the cell, i.e., the central law, and then in 1961 proposed the triplet genetic code, so that the structure of the DNA molecule and the biological function of the DNA molecule are organically and organically integrated. /p>

This organic unification of the structure and biological function of the DNA molecule has also laid a molecular foundation for revealing the nature of genes. s. Benzer used E. coli T4 phage as a material to analyze the fine structure of genes at the level of the structure of the DNA molecule, and put forward the concept of cis-transgender (cistor), proving that the gene is a specific segment on the DNA molecule, and is an independent unit in terms of its function. an independent unit. However, this particular DNA segment contains many mutation sites, also known as mutons, which are the smallest units that can produce mutations after mutation. Recombination can occur between these mutation sites, so a gene contains multiple recombination units, also known as recombinants (recon), i.e., the smallest unit that cannot be separated by recombination. Theoretically analyzed. Each pair of nucleotides within a gene can lead to a mutation, and recombination can occur between every two pairs of nucleotides. It can be seen that a gene with how many pairs of nucleotides on how many mutants

mutants and the corresponding number of recombinants. But in reality, the number of mutants is less than the number of nucleotide pairs, and the number of recombinants is less than the number of mutants. In short, the cis-antipode doctrine breaks the "trinity" of the concept of the gene, the gene for a specific section of the DNA molecule order, that is, responsible for encoding a specific genetic information of the functional unit - cis-antipode. However, it is internally divisible, containing multiple mutations and recombination units.

(V) Manipulator model 1961 French molecular biologists F. Jacob and J. Monod studied the role of genes through different E. coli lactose metabolism mutants, and put forward the manipulator model doctrine (operon theory). This doctrine elucidates the role of gene regulation in lactose utilization. That is, the genes involved in biological activity are organized together for uniform regulation and the precise proportion of each gene product is maintained. The prokaryotic manipulator system is the most efficient and economical expression of regulation at the transcriptional level. This model of regulation was epoch-making in the history of biological development and laid the foundation for the revelation of the difficult problem of gene expression regulation. As a result, they were awarded the Nobel Prize in 1956. In addition, they proposed that ribosomes do not contain templates responsible for the sequential assembly of amino acids, arguing that each DNA cis-transon gives rise to the synthesis of an RNA molecule with a limited lifespan, and that in the nucleotide sequence of this RNA, information about the amino acid sequence is contained. Subsequent binding of this RNA to the ribosome gives the ribosome the ability to synthesize a particular protein, thus further clarifying the role of genes and the central law of transfer of genetic information, as confirmed by a large number of experiments.

(F) "jumping genes" and "breakage genes" discovery For diploid higher organisms, the minimum number of chromosomes that can maintain the normal function of the gametes or gametophytes is called a genome. A genome contains a complete set of genes. For most prokaryotes, which have only one chromosome, the entire chromosome is a genome. Before the 1950s it was thought that the DNA in each genome was fixed. It consists of a series of genes with fixed numbers, fixed locations and fixed functions. In 1961, the discovery of E. coli lactose manipulator showed that functionally related structural genes are often tightly arranged together, indicating that the chromosome of Escherichia coli is not a randomly arranged collection. in the early 1950s, B. McClintock in the study of maize control factors have pointed out that some genetic factors can be shifted position. In the late 1960s, insertion sequences were found in E. coli. Then in the eukaryotic and prokaryotic organisms found in the genome of certain components of the position of the immobility of a common phenomenon, well will be able to transfer the position of these components known as jumping gene (jumping gene), also known as transposition factor (transposon element). In addition, the traditional view that a structural gene is a continuous piece of DNA sequence, the late 70s found that the vast majority of eukaryotic genes are discontinuous, which is separated by some non-coding sequences, so it is called broken genes. 1978, in phage also found overlapping genes, a gene sequence can be contained in another gene, two gene sequences may partially overlap.