Diagram showing DNA with a tandem repeat detected in parent, and expanded in the child

Tandem Repeat Expansions

Tandem repeats (TRs) are a class of DNA sequence where two or more bases are repeated immediately adjacent to one another. Expansions of these repetitive regions are suspected to contribute to the genetic etiology of complex disorders.

Short-read whole-genome sequencing (WGS) has trouble characterizing these regions due to ambiguous mapping. We are developing and implementing new technologies and computational algorithms to perform genome-wide screens of repetitive DNA. Our aims are to genotype TRs on large genomic datasets as well as determine the role, and characterize the mechanism, of TR variation.

blue cartoon brain

​Whole Genome Sequencing Analysis of Neurological Disorders

Many neurological disorders have a complex genetic origin, meaning the same, single gene cannot explain the phenotype for most cases. We carry out WGS analysis to investigate different forms of rare genetic (including single nucleotide, copy number, and TR) variation in neurological disorders, such as autism spectrum disorder, movement disorders, epilepsy, and schizophrenia.

Participate in our research!

We are actively recruiting participants with unexplained pediatric-onset movement disorders for a whole genome sequencing study. Check out our study poster or expand the section below to learn more.

Do you or your child have a childhood-onset movement disorder with no known cause?

In this study, we will look at your DNA to try and find an explanation for the disorder.

What is involved?

A blood draw, saliva sample or cheek swab to get your DNA.

If you are interested in learning more and/or taking part in this study, please contact Ian Backstrom at ian.backstrom@sickkids.ca or 416-813-7654 ext. 309663

2 diagrams: one showing a section of a chromosome being duplicated, the second showing the same duplication with x's on other parts of the chromosome to indicate genetic modifiers

Genetic Modifiers

Pathogenic genetic variants often exhibit incomplete penetrance and variable expressivity. Additional genetic factors (e.g., single nucleotide variants, copy number variants, structural variants, and TR expansions), which may act as modifiers, are sometimes present in affected individuals. We are studying this phenomenon in a number of disorders, including the 7q11.23 duplication syndrome, the 22q11.2 deletion syndrome, and in TR expansion related diseases such as motor neuron disease.