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UBC Theses and Dissertations

Genetic analysis of dyslexia Tzenova, Jordana


Dyslexia is a complex trait, which manifests as a specific reading and spelling disability that is independent of general intelligence and educational opportunity. A genetic basis for the trait has been clearly established, leading to the identification of eight dyslexia susceptibility loci to date. The aim of this thesis is to gain more insight into the genetic mechanisms underlying dyslexia by looking at variation at a single locus, variation at multiple loci, and by examining a phenotype that is thought to be co-morbid with the trait in a sample of 100 dyslexia families. The results of the first part of the study indicate evidence for linkage of dyslexia to chromosome Ip34-p36. This finding replicates the results from two previous reports, suggesting that a locus in this region may contribute to a significant proportion of dyslexia cases. The results of the second part of the study indicate evidence for the involvement of a multilocus genetic system in dyslexia. Both previously identified dyslexia susceptibility loci that do not have significant single-locus effects on the trait in our sample, and novel candidate gene regions show evidence for gene-interactions and locus heterogeneity. Finally, an examination of handedness genetics in dyslexia families was unable to replicate the findings of a recent genome-wide scan. There was no evidence to suggest that dyslexia susceptibility loci are involved in the genetic component of handedness, however the results implicate a novel region, 6q25.3, in relative hand skill determination.

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