Genetic research technology

Drosophila is a popular model organism in genetic research.

At first, geneticists studied a wide range of subjects, but gradually concentrated on the genetics of certain species (model organisms). This is because new researchers tend to choose some organisms that have been widely studied as research targets, making model organisms the basis of most genetic research. Genetic research of model organisms includes gene regulation and research on genes related to development and cancer.

Model organisms have the advantages of short passage time and easy gene manipulation, which makes them a popular tool for gene research. At present, the widely used model organisms include Escherichia coli, Saccharomyces cerevisiae, Arabidopsis thaliana, Caenorhabditis elegans, fruit flies and mice. The purpose of medical genetics is to understand the relationship between gene variation and human health and disease. When searching for unknown genes that may be related to diseases, researchers usually use genetic linkage and genetic pedigree to locate disease-related regions in the genome. At the population level, researchers will use Mendelian random method to find disease-related regions in the genome, which is especially suitable for polygenic traits that cannot be defined by a single gene. Once the candidate genes are found, it is necessary to do more research on the corresponding genes (orthologous genes) in model organisms. For the study of genetic diseases, more and more techniques for studying genotypes have also been introduced into pharmacogenetics to study how genotypes affect drug responses.

Although cancer is not a genetic disease in the traditional sense, it is considered to be a genetic disease. The process of cancer in the body is a comprehensive event. There is a certain probability that cells in the body will mutate during division. Although these mutations will not be passed on to the next generation, they will affect the behavior of cells and in some cases lead to more frequent cell division. There are many biological mechanisms to prevent this from happening: signals are transmitted to these abnormally divided cells and cause them to die; But sometimes more mutations make cells ignore these signals. At this time, natural selection and gradual accumulation of mutations in the body make these cells begin to grow indefinitely, thus becoming cancerous tumors (malignant tumors) and infecting various organs of the body. Escherichia coli colony on agar plate is an example of cell cloning, which is often used for molecular cloning.

You can manipulate DNA in the lab. Restriction endonucleases is a commonly used enzyme, which cleaves specific sequences and is used to prepare predetermined DNA fragments. Then these fragments are reconnected by DNA ligase, and the recombinant DNA can be obtained by connecting DNA fragments from different sources together. Recombinant DNA technology is usually used in plasmids (short circular DNA fragments containing a few genes), which is usually related to the manufacture of transgenic organisms. Plasmids are transferred to bacteria, and then these bacteria are grown on agar plates (colony clones are isolated), and then researchers can use the cloned colonies to amplify the inserted plasmid DNA fragments (this process is called molecular cloning).

DNA can also be amplified by a technique called polymerase chain reaction (also called PCR). Using specific short DNA sequences, PCR technology can separate and amplify the target region on DNA. Because amplification requires only a very small amount of DNA, this technique is often used for DNA detection (detecting the presence of specific DNA sequences). DNA sequencing technology is the most basic technology developed in genetic research, which enables researchers to determine the nucleotide sequence of DNA fragments. The chain termination sequencing method developed by frederick sanger and his colleagues in 1977 is now a routine means of DNA sequencing. With the help of this technology, researchers can study DNA sequences related to human diseases.

Because sequencing has become relatively cheap, and with the help of computer technology, a large number of different fragments of sequence information can be connected (this process is called "genome assembly"), many organisms (including humans) have completed genome sequencing. These techniques were also used to determine the human genome sequence, which led to the completion of the human genome project in 2003. With the development of new technology in high-throughput sequencing, the cost of DNA sequencing is greatly reduced. Many researchers hope to reduce the price of measuring a person's genome information to less than 1000 dollars, thus making large-scale sequencing possible.

A large number of measured genome sequence information gave birth to a new research field-genomics, and researchers used computer software to find and study the laws existing in the whole genome of organisms. Genomics can also be classified as a field under bioinformatics (using computational methods to analyze biological data).