The main provisions of the program "Human Genome "
Once created program "Human Genome", the three main objectives of this program have been identified: the creation of accurate genetic map, the creation of a physical map of the human genome and sequencing (determining) the entire human genome.
genetic genome map the exact genetic map can be created when two conditions are met: detecting in the genome of a large number of polymorphous (diverse) genetic markers and the presence of a sufficient number of families for linkage analysis between these markers and the establishment of their mutual arrangement.The problem of genetic markers has been resolved after the discovery of different types of DNA polymorphisms.In order of their introduction to genetic analysis was first detected as restriction fragment length polymorphism (RFLP for short), then the polymorphism due to varying numbers of tandem repeats (VNTR-polymorphism).Each of these types has its own advantages and disadvantages, but all together they allow to label the human genome with a ve
Even the first 4 types of polymorphisms helped to create a genetic picture of the human genome.Set the relative position of markers allowed the collection, or the bank, cell lines derived from all members of a few hundred families, which included at least three generations.This bank of cell lines was created in France for the study of polymorphism in the HLA system and is very useful for genetic mapping of the human genome.After each chromosome was mapped and found the relative position of 10-15 polymorphic markers work with further markers carried on the material received from the members of these families.
genome map To create a physical map of the genome, the cloned fragments of the human genome also had to mark.This was done via short of sequences (DNA regions with already defined sequence), so-called the STS, chromosomal localization of which is precisely known.STS easily identified by polymerase chain reaction (PCR).Received more than 50,000 STS.scattered throughout the genome, and during physical mapping is established when the mutual arrangement of DNA fragments from genomic libraries used as the STS markers overlapping DNA segments.
definition of the human genome
Below we summarize the main results of the "draft version" of the human genome, which, as noted above, were published in the February issue of the journal «Nature» in 2001
term "draft" beforeonly refers to the fact that the genome determination continues.In this regard, at present it is impossible to arrange the study in order to orient and sequenced many small sequence.Incomplete sequencing, of course, is creating problems for the identification of genes of hereditary diseases, unique genes and other genetic structures.
should be noted that in the last quarter of XX century.599 were sequenced genomes of viruses or other microorganisms like and macroorganisms (animals).The experience gained as a result of this work, it has been fully used in the sequencing of the human genome.
human genome study of strategy in public projects include the production of a genetic and physical map of the human genome, the subsequent introduction of these cards results of sequencing individual clones of genomic DNA (sequencing strategy "clone of a clone").The physical map of the human genome is a clonal basis, which was developed by scientists Olson in 1981. The approach is as follows.Gene was cut into segments by partially digesting enzymes - specific endonucleases.These large DNA segments were placed in bacterial artificial chromosome (BAC) and introduced into the bacteria, where they are copied at each division bacteria.The resulting clones formed identical DNA molecules.Such clones spanning the human genome, should be about 20 000.
addition, for establishing the order of the clones used previously developed maps STS.The result is a physical map of the genome.Selected BAC clones were cut into fragments and cloned.The resulting clone subclones fragments studied.Every time determined by a large number of subclones of the same, to make sure that every piece of the original BAC clones analyzed several times and not allowed errors.Sequencing of individual fragments were pooled in order to obtain a sequence of nucleotides in each BAC clone source.Finally, sequencing the entire genome of sequences collected by connecting a set of BAC, covering the entire genome.Thus created a map of the human genome sequencing has more than 1,000 ruptures.This may be due to several reasons, including the fact that the original BAC clones covering the entire genome, as well as the overlap between the clones was skipped due to the presence of large repeats in the genome.Established as a result of the project sequencing map includes sequences containing an average of a few million base pairs in length.Segments such a length sufficient to map based on the clones, to impose on other cards with a lower resolution.The position on the genetic map of the sequenced sequence is defined as a relatively mapped STS.
In general, sequenced and assembled with the help of computer programs in stretches of about 90% euchromatin regions of the genome.
Despite the incompleteness of sequencing, a number obtained with the help of the results now of undoubted interest.This applies primarily to the deepening of ideas about the organization of the human genome.