Question

It is now accepted that the origin of autism is linked to

A. Expectant mothers who drink excessive amounts of alcohol

B. Exposure to smoking while in the womb

C. Illness during infancy

D. Genetic factor

Answer 1

It is now accepted that the origin of autism is linked to genetics.

Autism has a strong genetic basis, although the genetics of autism are complex.

Many genes have been associated with autism through sequencing the genomes of affected individuals and their parents.

Studies of twins suggest that heritability is 0.7 for autism and as high as 0.9 for ASD, and siblings of those with autism are about 25 times more likely to be autistic than the general population.However, most of the mutations that increase autism risk have not been identified

. Typically, autism cannot be traced to a Mendelian (single-gene) mutation or to a single chromosome abnormality, and none of the genetic syndromes associated with ASDs have been shown to selectively cause ASD.Numerous candidate genes have been located, with only small effects attributable to any particular gene.Most loci individually explain less than 1% of cases of autism.

The large number of autistic individuals with unaffected family members may result from spontaneous structural variation—such as deletions, duplications or inversions in genetic material during meiosis.

Hence, a substantial fraction of autism cases may be traceable to genetic causes that are highly heritable but not inherited: that is, the mutation that causes the autism is not present in the parental genome.

Autism may be underdiagnosed in women and girls due to an assumption that it is primarily a male condition,but genetic phenomena such as imprinting and X linkage have the ability to raise the frequency and severity of conditions in males, and theories have been put forward for a genetic reason why males are diagnosed more often, such as the imprinted brain theory and the extreme male brain theory.