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Introduction to Biochips DNA molecules exist in a double-stranded form in most organisms (with the exception of a few viruses, bacteriophages). Under certain special physiological conditions, such as cell division, gene expression, etc., the double-stranded DNA will be unwrapped into a single strand and then returned to double strands. Biologists have long used this property of hydrogen bonding to form a double-stranded DNA molecule in biologically relevant research, called hybridization. Since 1965, Gillespie and Spiegelman published the use of heterozygous reactions to screen recombinant strains, there are many experimental techniques, including Southern blot, Northern blot, in situ Hybridization, DNA Sequencing, PCR (Polymerase Chain Reaction) and even the current popular biochips (DNA chips) are all based on the principle of nucleic acid hybridization. From this historical evolution, we can also see the multi-potential potential of biochips in genomic research. Biochips are first known as single-strand DNA molecules, called probe DNA, which are immobilized on nylon membranes, glass or other solid carriers by chemical covalent bonding or physical adsorption. on. Some experimental techniques are used to replicate or amplify genes or DNA fragments of interest from cells or bacteria, called target DNA, and label them with fluorescent substances. After the target DNA and the probe DNA on the chip are heterozygous, if the cell or bacteria have a gene or DNA fragment on the implanted chip, fluorescent highlights can be detected on the scanner, and we can know which genes. There are performances, which genes are not showing. Different from the probe DNA on the implanted chip, it can be divided into two categories: one is to implant a single-stranded cDNA into a chip, which is called a cDNA chip; the other is to implant an oligonucleotide sequence. Into the chip, called the oligo chip. These two types of biochips are different in nature and are suitable for different genome studies and extend the range of biochip applications. The application of biochips in genomic research and the rapid and large-scale processing of samples at the same time are the biggest advantages of biochips. At present, the field of biochip research is widely used, such as: gene expression, discovery of new genes, cancer classification, new drug development. , single nucleotide polymorphism (SNP), and the like. 1. Gene Expression Before the development of biochips, most researchers were limited to the study of the performance of one or several genes. For complex biological systems, it is no different than to look at the sky. With biochips, we can monitor the performance of hundreds or even thousands of genes at the same time. Affymetrix's Human Genome U95 Set contains more than 6,000 human genes and EST fragments, which cover almost all human genes. With this biochip, we can transfer the entire reaction mechanism and signal to the organism. Transduction) has a more complete understanding. In the case of cancer, cancer has been the top ten cause of death for humans. For biologists, it is also an interesting and complicated topic. Why do some people get cancer? Some will not? What causes a normal cell to start unrestricted and split? Although tumor suppressor genes and oncogenes have been found so far. But cancer is the result of a combination of many factors. It is difficult to determine what carcinogens are causing cancer. Because it involves the interaction of many genes, the causes have not been known so far, let alone treatment. . Biochips provide a great tool to tell us how cancer cells differ from normal cells. We extracted its mRNA from normal cells and made its complementary DNA (cDNA) with reverse transcriptase and labeled it with green fluorescent substances. Similarly, the cDNA extracted from cancer cells was made into red fluorescence after making cDNA. Material calibration, the two standard DNAs (this refers to cDNA) are mixed on the same chip for hybrid reaction, the genes with more normal cells show green dots, while the genes with more cancer cells show red dots, normal cells and Genes with the same expression of cancer cells show yellow spots. This will tell which genes are abundantly expressed in cancer cells. In this case, the ErbB2 gene exhibits a red dot indicating that the gene is abundantly expressed in breast cancer cells. This method can be applied to a variety of other research fields, for example: Lockhart uses a biochip containing 65,000 oligonucleotide probes to analyze 114 genes in mouse T cells. It was found that under the induction of cytokine, 20 genes were affected. Kevin et al. used 6240 biochips with different genes and EST fragments to study genes related to metamorphosis. Using a biochip containing 6,400 DNA fragments, Joseph studied the genetic behavior of yeasts from respiration to fermentation, and about 710 genes were induced when glucose was gradually reduced in culture. 1030 genes The product is reduced. 2. The discovery of new genes can be seen from the above, whether it is the expression of cancer cells, the stimulation of T cell responses, the development of Drosophila, or the changes in metabolic pathways. These physiological phenomena are regulated by complex genes and involve many genes. Estimated by about 100,000 genes in humans, we know that the genes of its function are less than 5%, and there are only a handful of people who really know the mechanism of action. There are a lot of probe DNAs on the chip, but we don't know the function, but when we look at the gene expression of the whole cell, we can do some genes that are unclear but are promoted or inhibited. In-depth research, and speculate that it is involved in that signal path. Taking Joseph's experiments on yeast metabolism as an example, more than 400 new genes were discovered. 3. Classification of Cancer Traditionally, pathologists have classified them according to the type of tumor, but this classification is not effective for those cancers with similar histopathology, but with different disease duration and later healing. Now scientists can use biochips to classify cancer. Molecular diagnosis not only accurately distinguishes similar cancers, but also gives us a better understanding of the molecular mechanisms of tumors. Golub published in the 1999 Science Journal using biochips to distinguish between Acute Myeloid Leukemia (AML) and Acute Lymphoblastic Leukemia (ALL). These two types of blood cancer (Leukemia) are similar in microscopic morphology, but require completely different chemical treatments. First, they used a 6800 gene chip to examine 38 patients (27 of which were diagnosed as ALL and 11 were AML), and then locked in 50 genes, including cell surface antigens. Cell cycle protein, cell adhesion protein and some enzymes. These 50 genes clearly differ in AML and ALL. It can therefore be used to distinguish between AML and ALL. The detection of cancer by biochip is not only a major breakthrough in cancer diagnostics, but also has a major impact on the development of cancer treatment and cancer suppressing drugs. 4. The general strategy for the development and development of new drugs for new drugs is to find cell markers (usually proteins) that are specific to the disease, and then screen for molecules that inhibit or compete for the protein—possibly proteins, nucleic acids, or organic compounds. However, this method is limited to screening only known cell targets, and the biochip can accelerate the identification of specific cell targets of the disease and show its pathological action pathway. These findings can be immediately used in the development of new drugs. For example, Her-2/neu is abundantly expressed in breast cancer cells, and it has the potential to become the target of new drugs. In other words, we can find some molecules that inhibit the expression of Her-2/neu - that is, new drugs. In addition, new drugs under development can also use biochips to understand its mechanism of action. 5. Single nucleotide polymorphism (SNP) Although the chromosomal differences of the same species are extremely small, there is one mutation in the average of 1000 base pairs. These mutations are called SNPs and cause everyone to take drugs. The reasons for different sensitivity and different blood types. In addition, SNPs are also associated with diseases such as cancer, cardiovascular disease, autoimmune, diabetes, and Alzheimer's disease, and even microbial resistance. So the SNP is now getting more and more attention. The SNP Association, TSC (The SNP Consortium), planned to spend $45 million in April 1999 to find 300,000 SNPs in two years and build a database. Recently, many researchers want to use high-density biochips to identify human SNPs. Patrick et al. use current-capable semiconductor biochips to distinguish human SNPs from human Mannose Binding Protein (MBP). MBP is important for the innate immune system, especially for children who have not yet developed a complete immune system. In addition, Affymetrix has also developed p53GeneChip, which is designed to detect the SNP of the base sequence of the tumor suppressor gene p53 in a specific region by designing a probe DNA containing five different base sequences (A or G appears) ); HIV GeneChip can detect HIV-1 Protease mutations. The most important biomedical research tool of the 21st century is the US-led Human Genome Project, which is expected to solve all 23 pairs of human chromosome DNA sequences in 2003, with an estimated 100,000 genes and 300 million bases. Correct. The vastness of the project is one of the great achievements of modern humans with the 1969 Apollo mission to the moon. Because humans have evolved since 3.5 million years ago, the first complete knowledge of the genetic code they carry, especially the understanding of the disease, will have a breakthrough. In addition to the human genome program, more than 600 species of chromosomal DNA sequences have been solved, including bacteria, viruses, eukaryotes (fruit flies, nematodes, Arabidopsis, etc.). Every day, a new DNA sequence is solved. Such a huge DNA sequence is like a book of four letters A, T, G, and C. For the meaning hidden in it, It is necessary to rely on bioinformatics to decode it into "genes" that we can understand. Further, we need biochips to tell us that the regulation of genes in the whole body is physiological, pathological or pharmacological, so that we have a whole view of biology. understanding.
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