It has long been assumed that there is a common cause of genetic levels, cognitive and neural autism are characteristic triad of symptoms. But there is a growing suspicion that autism is a complex place, including the key elements have different causes, which are often co-occur.
Three diagrams of pairs of chromosomes A and B, which are almost identical. 1: B lacks a segment of A. 2: B has two copies of an adjacent segment of A. 3: B copy of a segment in reverse order.
Exhaust (1), duplication (2) and reverse (3) are all chromosome abnormalities that are implicated in autism.
Autism has a strong genetic basis, although the genetics of autism are complex, and it is unclear whether ASD is explained more rare mutations in a significant impact on multigene interactions are rare or common tradition.The complexity arises because of interactions between different genes, epigenetic and environmental factors, which do not alter DNA, but are inherited and affect gene expression. [20] Studies of twins, the heritability is 0.7 and even 0.9 Autism: ASD, autism and the brothers who are about 25 times more likely to be autistic than the general population. However, most mutations that increase the risk of autism have not been identified. Typically, autism can not be traced back to Mendelian (single gene), a single mutation or chromosome abnormality, such as fragile X syndrome, and none of the genetic syndromes associated with the development of large-scale disturbances have been found to cause selectively ASD.
Many candidate genes have been located, with only small effects attributable to a particular gene. The large number of people with autism affected family members may arise from spontaneous variations in copy number, deletions or duplications in genetic material during meiosis. Therefore, a significant fraction of cases of autism may be attributable to genetic causes that are highly heritable but not inherited:. is the mutation that causes autism is present in the genome of the parents
Several lines of evidence point to synaptic dysfunction as a cause of autism. Some rare mutations may lead to autism by disrupting certain synaptic pathways, such as those involved in cell adhesion. [66] Studies of a gene replacement in mice suggest that autistic symptoms are closely related to the later stages of development, which depend on the activity of synapses and changes in activity-dependent. All known teratogens (agents that cause birth defects) related to the risk of autism appear to act in the first eight weeks of conception, and although this does not exclude the possibility that autism can be initiated affected or later, there is strong evidence that autism arises very early in development.
Although evidence of other environmental causes is anecdotal and has not been confirmed by reliable studies, , extensive research is ongoing. [68] Environmental factors that have been claimed to contribute to or aggravate autism, and may be important in future research, including certain foods, infectious diseases, heavy metals, solvents, diesel exhaust, PCBs, phthalates and phenols used in plastic products, pesticides, brominated flame retardants, alcohol, tobacco, illegal drugs, vaccines and prenatal stress , even if no link is found, and some were completely DIS-proven.
Getting parents to be aware of the symptoms of autism in their children at the time of vaccination. This has led to unsupported theories blaming the vaccine "overload" the preservation of vaccines and autism, the MMR vaccine causes. The latter theory was supported by a study funded by the dispute has since been shown to have been "an elaborate fraud." Although these theories have no convincing scientific evidence and are biologically plausible , the concern of the parents of a candidate vaccine link to autism has led to reduced rates of childhood vaccination, epidemics of childhood diseases and controlled in some countries, preventable deaths of children from several.
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