Front Matter

24 Introduction to Autism Spectrum Disorders

exposure to environmental pollutants [8–13,43,49]. In contrast, studies involv­

ing genome‐wide and targeted microarrays have revealed substantial de novo

CNVs that were meaningfully enriched among the proband (this term is used

for the persons who are the original or index point for a genetic disease or a

study subject) under consideration when they were compared with controls or

siblings unaffected by ASD [85–88]. Comparative studies, using both subse­

quent and initial higher resolution methodology, have found a de novo CNV

level of approximately 8% for sporadic ASD patients, while the level for unaf­

fected siblings is only about 2% [87]. Moreover, for children who experience

general developmental delay and also ASD, the level of de novo CNVs may

reach as high as 15% [8–12, 87]. Again, this points to a different cause or causes

of ASD. We believe these are synthetic chemicals.

More Than 1,000 Genetic and Genomic Disorders and Still Counting

We have asserted that ASD is regarded as a disorder that is heritable; still, stud­

ies of candidate gene association, CNV, and genome‐wide association have not

yet located a single causative gene, a single nucleotide, or a single CNV that can

Exome sequencing

Exons

Exome

Transcription, elimination

of intron transcript

segments, and spilicing

of exons

Figure 1.13 Illustration showing how the exomes are assembled and exome sequencing is

carried out. Only ~1% of human genomes contain exons. In exome sequencing all the exons

are joined together into one large assembled format and then sequenced. The exome

represents all the genes that direct the production of thousands of proteins. Source: https://

d2gne97vdumgn3.cloudfront.net/api/file/AuHulxYbQ46mPuuqdJ6H. (See insert for color

representation of this figure.)