Genetic mapping
Genome mapping is a method by which we obtain the most accurate picture of genových mapách. The basis of mapping is to determine the number of chromozom, positions gen on given chromosomes and in what order the genes are located (gene distance). Determining the exact sequence is possible using genome mapping methods and sekvenování genomu.
One of the main tasks of medical genetics is to identify genes, determine their function, and detect changes that cause disease - a prerequisite for this is gene mapping. K mapování lidského genomu jsou využívány dvě metody:
- genetic mapping
- uses the frequency of meiotic crossing-overs to estimate the distance between loci
- physical mapping
- uses cytogenetic and molecular genetic techniques to precisely localize on the chromosome
Mapping the genome[edit | edit source]
We are able to determine the number of chromosomes using common methods cytogenetického vyšetření karyotypu. The laws of gene linkage and three-point experiment are used to determine the order and distances of genes. Iron Iron Other mapping methods include, for example, the hybridoma method and probe mapping.
Hybridoma method[edit | edit source]
It was used in the past, but nowadays it is rather abandoned. The method is too lengthy and requires experience.
Successful experiments were carried out with hybrids of mice and human cells. Mouse lines with a deficiency of a certain enzyme were selected, the function of which was completely taken over by the corresponding human gene in the offspring. These hybrids tended to eliminate human chromosomes. The evaluation was carried out by monitoring the presence of the product of the given chromosome. If only one human chromosome remained in the cell and its product was also present, the gene was localized to this chromosome.
This method succeeded in localizing the gene komplex HLA systému human according to its antigenic products and translokace to the distal part of the p-arm of chromosome 6.
Probe mapping method[edit | edit source]
If we know the protein product of a gene, we can try molekulární sondu. We will assemble a sequence of nucleotides that encode the frequency of the gene under investigation and we can try mutual hybridization.
In modification DNA-RNA A strand of mRNA labeled with a radioactive isotope is used. The base labeled with the isotope hybridizes to the part of the DNA where the structural gene is responsible.
Sequencing methods[edit | edit source]
The Sanger and Maxam & Gilbert methods were developed to determine the exact sequence of nucleotides in DNA. The Sanger method is more widely used today.
Sanger method[edit | edit source]
náhled|350px|vpravo|Sangerova metoda sekvenování, 5'TACAGTTTCAGGA3' It uses the special properties of special nucleotides - 2', 3' dideoxyribonucleotide triphosphates (ddATP, ddCTP, ddGTP and ddTTP), to the end of which another nucleotide cannot be attached.
We amplify single-stranded DNA, add DNA polymerase, the appropriate primer and enough deoxyribonucleotide triphosphates (dATP, dCTP, dGTP and dTTP) (for synthesis) and some amount of another type of dideoxyribonucleotide triphosphate (e.g. ddATP). The primers are attached to single-stranded DNA and the polymerase completes the sequence of the other strand. When dATP is added to the chain, there is a certain probability that it will complete ddATP, which will terminate the polymerization. Such a product will end with adenine. In the case of the reaction taking place with ddCTP, ddGTP and ddTTP, we will obtain a mixture of oligonucleotides terminated with the appropriate base.
We will then carry out elektroforézu dané směsi. We perform electrophoresis evaluation from the bottom and evaluate the DNA sequence.
Iron Iron
Maxam & Gilbertova[edit | edit source]
Uses specific chemical cleavage of DNA after certain nucleotides instead of a polymerization reaction. Evaluation is performed electrophoretically, as in the Sanger method.
Mapping Results[edit | edit source]
By knowing the exact sequences, we are able to identify the origin of the disease. We can knock out the gene that causes the disorder by targeted mutation.
For ethical reasons, such experiments cannot be performed on humans! náhled|200px|vpravo|Genomická mapa
Genetic Maps[edit | edit source]
Based on základu vazebné analýzy. The meiotic crossing-over frequency is used to estimate the distance between two loci.
The distance of the respective genes on the chromosome (recombination fraction) is expressed using the Morgan number:
Morgan's number is expressed in centimorgans [cM]. náhled|200px|vpravo|Fyzická mapa HLA komplexu
Physical maps[edit | edit source]
Helps determine the exact location of genes in a DNA sequence. The distances between genes are expressed in base pairs. This method uses a technique cytogenetických and molekulárně genetic.
