Biochemistry and Molecular Genetics of Speech–Sound Disorder and Dyspraxia


In this review, some of the most exciting recent developments in the biochemical and molecular genetic research on common learning disabilities (LD) such as speech–sound disorder (SSD) and dyspraxia have been summarised. A greater understanding of biochemical abnormalities (galactosaemia or polyunsaturated fatty acids deficiency) may provide a useful addition with other treatment procedures for these LD or improving learning abilities for them.

This review also highlights the genetic contribution to SSD and dyspraxia. These disabilities influenced by genes and several research groups to attempt to identify susceptibility and candidate genes of those through the sequential analysis of genetic linkage and association. Currently, genetic linkage studies have identified one susceptibility locus on 3p12–q13 associated with SSD, and also one susceptibility locus (speech–language disorder 1; SPCH1) on 7q31 and two candidate genes (FOXP2 gene on chromosome 7, and FOXP1 gene on chromosome 3) have been found associated with dyspraxia.

Key Concepts:

  • Learning disabilities may cause the learner to understand or to use language (spoken or written) with an imperfect ability to listen, think, speak, read, write, spell or do mathematical calculations.

  • Speech–sound disorder (SSD) is characterised by the substitution or emission of speech sounds leading to intelligible speech.

  • Individuals with dyspraxia seem to have problems in production of speech sounds due to poor motor skills (articulation), and applying linguistic rules to combine sounds to form words (phonological).

  • Biochemical and molecular genetic studies of learning disabilities may help us to understand the relationships between specific pattern deficits contributing to disordered learning. Moreover, greater understanding of biochemical abnormalities of these disabilities may provide a useful addition with other treatment procedures for them.

  • Genetic factors are important in SSD and dyspraxia.

  • Molecular genetic researches should be aimed to identify susceptibility and candidate genes for SSD and dyspraxia.

  • Molecular advances in SSD and dyspraxia will help to set the research agendas for future studies to follow.

Keywords: learning disabilities; speech–sound disorder; dyspraxia; association; linkage; SPCH1; FOXP2; FOXP1


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Further Reading

Caylak E (2009) Neurobiological approaches on brains of children with dyslexia: review. Academic Radiology 16(8): 1003–1024.

Caylak E (2010) The studies about phonological deficit theory in children with developmental dyslexia: Review. American Journal of Neuroscience 1(1): 1–12.

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Caylak, Emrah(Aug 2011) Biochemistry and Molecular Genetics of Speech–Sound Disorder and Dyspraxia. In: eLS. John Wiley & Sons Ltd, Chichester. [doi: 10.1002/9780470015902.a0023689]