Heredity is an important topic in the autism discussion. Considering the causes of autism spectrum disorder and being able to pinpoint an answer to the question of how a person is diagnosed will lead you to the topic of its hereditary components.
The ability to acquire autism through hereditary means can be explained through genetic variation. If the conditions of the variation is high, then it can be explained as a primarily genetic condition. Many of the genes found to be associated with autism spectrum disorder are involved in the function of the chemical connections between brain neurons or synapses. Researchers are looking for clues about which genes contribute to increased susceptibility. However, as we research further, it is not clear whether autism can be explained through the process of gene mutations or through multi gene interactions. To add to the theory that genetic variations that are produced genetically and are located within a person’s cell makeup, current research has also determined that spontaneous gene mutations can contribute to the risk of developing autism spectrum disorder. These mutations are changes in sequences of DNA, the hereditary material in humans. The mutation then occurs in each cell as the fertilized egg divides. The mutations may affect single genes or there may be changes called copy number variations, in which stretches of DNA containing multiple genes are deleted or duplicated. Recent studies have shown that people with autism spectrum disorder tend to have an increase in copy number gene mutations than those that have not been diagnosed with the disorder, suggesting that for some, the risk of developing autism is not the result of mutations in individual genes but rather spontaneous coding mutations across many genes. Spontaneous mutations may explain genetic disorders in which a child that is affected with autism has the mutation in each cell but the parents do not and there is no family pattern to the disorder. Autism risk also increases in children born to older parents. There is still much research to be done to determine the potential role of environmental factors on spontaneous mutations and how that influences autism spectrum disorder risk.
In some cases, parents and other relatives of a child with ASD show mild impairments in social communication skills or engage in repetitive behaviors. Evidence also suggests that emotional disorders such as bipolar disorder and schizophrenia occur more frequently than average in the families of people with ASD.
Early in the process of researching Autism, some studies were completed on twins. The results estimate that the heritability of autism to be in the range of 90%. This means that the differences observed in autistic individuals compared with those of non-autistic individuals was due to genetics. However, this may be an overestimated statistic. New studies indicate that when one twin is diagnosed with Autism, the other twin is often diagnosed with a learning or social disability. For an older siblings, there may be a diagnosis of autism and that likelihood could be as high as 30%, which is much higher than the risk in controls. This seems to indicate that there needs to be more twin studies completed to achieve the data necessary. In other words, the current data for genetic analysis has been inconclusive as more than one gene may be implicated in the individual mutations.
Twin and family studies strongly suggest that some people have a genetic predisposition to autism. Identical twin studies show that if one twin is affected, then the other will be affected between 36 to 95 percent of the time. There are a number of studies in progress to determine the specific genetic factors associated with the development of ASD. In families with one child with ASD, the risk of having a second child with the disorder also increases.
Additional Genetic Markers
Research completed in family studies have located numerous candidate genes that encode proteins involved in the function of neurodevelopment. However, the mutations that had been indicated in a risk for autism were not identified. Currently, autism cannot be traced to a single gene mutation or to single chromosome abnormalities. It could be indicated through several mutated genes or a combination of the environment and mutated genes. There have been a combination of genes that have been discovered that encode proteins. The large number of autistic individuals with unaffected family members may result from copy number variations, spontaneous alterations in the genetic material during meiosis that delete or duplicate genetic material.
Sporadic and cases not dealing with an inherited value have been examined to identify genetically caused specifics involved in autism. A substantial fraction of autism may be highly heritable but not inherited: that is, the mutation that causes the autism is not present in the parental genome.
The research that has been completed on the hereditary component of autism spectrum disorder is very instrumental in predicting a cause of the disorder. According to the data, the research has the ability to help us recognize that there is a genetic component involved, even though it doesn’t tell the whole story. Paying attention to this component enables us to come closer to discovering a cause of autism spectrum disorder. In doing so, we can also create ways to better assist and offer support to those on the spectrum.
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