Triplet Repeat Instability repeat beyond the normal threshold stable, instability of triplet repeats, nucleotide repeat of a particular gene, genetic disease caused by a type of mutation to be the same for the entire gene It is a set of. Mutation is a subset of unstable microsatellite repeat that occur in the genome sequence of all. It is possible that multiplies the number of causes defective gene if repeatedly exists a dynamic mutation of healthy genes. , trinucleotide repeats, are classified as a separate class of mutation sometimes insertion mutation often.
Function of abnormal gene trinucleotide repeat of (TNR) disease is stimulated an important study of the molecular mechanisms underlying the instability of the repeat. Useful tools for studying unstable TNR, genetic analysis selective contraction and expansion, have been developed the yeast Saccharomyces cerevisiae in (Saccharomyces cerevisiae). These tests, and reproducible quantitative, win, easy to handle sensitive. Genetic selection using the exact molecular changes in the TNR tract in detail after the colony PCR, it has been confirmed by further experiments. In this chapter, analyze, and provide technical knowledge to help you create and test the instability of triplet repeat in the model system classic, it tells you these yeasts.
The array to make TNRs coding to deploy different from those of the non-coding region of development? Huntington’s disease (HD), through paternal transmission, an increase of pre-mutation allele repeat length (> 7 CAG) occurs almost exclusively in large and expanding range of disease. Even size similar to that extending allele or mother may not show change through the transmission of paternal likely to display shrinkage in CAG repeat size high offspring mother affected will. Small gains and losses was carried out through a series of generations, in men with pre-mutation allele close to threshold disease is inherited allele then, expansion has been favored by the contraction of 3-175 times. A similar pattern was observed in a mouse model of HD.
The timing of expansion of male reproductive HD is not clear, but it seems to occur at different stages of development of germ cells in both human and mouse. Variations in HD patients four CAG tube size was significant mature sperm of them, (differentiated into spermatocytes includes a section of haploid sperm cells) testis size tubes patients three with HD of There was minimal35 variation. Therefore, some extensions occurs later in the development of germ cells clearly. In fact, in the R6 / 1 mouse model of HD, expansion is most apparent in the number of meiotic cells36 second half. In the transgenic mouse model of HD and in HD patients, as expected if it occurs in spermatogonial germ cells expand extend throughout adulthood instability and does not correlate with the age of the father. However, cells that were laser-captured from the testicles, in the two patients that have a high resolution, it has been found in human primary spermatogonia, most of the extension of the length of the disease, an extension of the length of fewer sick is, I include cell population after meiosis (found in, but has been increased in the final population) the maximum TNRs. Meiosis in meiosis occurs clearly Rxpansions before to be completed in the germ cell differentiation or after section spermatogoni.
Somatic cell heterogeneity of people with HD and HD mouse model widely. May expand in humans occur with age, expansion is resumed in somatic tissues, with the mouse and continue the life of animals, the size of the alleles, stable 11 weeks from the 8-cell stage embryos 6 after birth have. In mice, that (FACS) occurs in the postmitotic neurons expansion fluorescence-activated cell sorting and laser capture, the degree of expansion is quite different brain regions and somatic tissues to confirm the analysis. In addition to the inheritance TNRs, post-mortem brain tissue extension of significant HD patients from brain cell body of CAG length of the tube to affect the appearance of the disease clearly.
The severity, trinucleotide repeat disorders, shows the expectation of genetic in general and increase in each generation that succeeded them, successive. Perhaps, this is described by adding additional CAG-repeat gene descendants of victims. Repeated CAG more genes, when encoding a protein HTT, for example, Huntington’s disease occurs. Is considered a “normal” mother with repetition will not be showing the symptoms of the disease. However, descendants of the parent will be the greater risk than the general population for developing such Huntington to add protein cause CAG codon cause production mHTT another (mutant HTT), a disease in itself. Huntington does not happen spontaneously most, it is the result of inheriting the defective gene from a parent who had one effect almost always. In particular, there is an increased risk if it is close to the number needed for the disease to manifest, it is one of those with a parent who has the number of CAG repeats quite gene itself of HTT already and cases, meet sporadic Huntington people, despite no history of illness of family, to develop Huntington’s being said. In addition, repeat more, is early-onset disease more severe. The early days, people with Huntington’s disease in a good family for a long period of time, of the disease, such as adding mutation extra CAG codon to be a lot of potential, such as the very onset of the disease shows a more rapid progression, and successive generations of each described reason.