Occasional errors in copying of the template, either single base changes or misreading the length of the repeat unit, would lead to abrupt switches in the repeating sequence.
The same was true when comparing length of the repeat tracts in clones sorted from different populations.
Depending upon the length of the repeat unit, the length of microsatellites varied from 14 to 86 bp.
Thus, GFP intensities, measured by flow cytometry, serve as a proxy for the length of the repeat tract (Supplementary Fig. 1A,B).
The length of the repeat region between the control region and tRNA-Phe is a minimum estimate, since the 454 sequencing reads did not span the region completely.
Thus, it appears that individuals with repeat expansions in ATXN2 can present with SCA2, parkinsonism, or ALS depending upon the length of the repeat.
Altering the length of the repeat region could then alter the interactions between the conserved N- and C-terminal domains, and so modulate the enzyme's catalytic properties, in particular its substrate specificity.
Intriguingly, select situations appear biased strongly toward one neurological outcome or another; interestingly, this may be influenced by not only the length of the repeat, but also the purity of the CAG repeat region encoding the polyQ expansion.
The basis of the detector algorithm is cross-covariance, and this function performs poorly if the detector window (set at 1 second in this program) does not match the actual length of the repeat to be detected.
To quantify this, we compared the mean, median and standard deviation of the length of the repeat elements in C19MC to the distribution of the same characteristics in the randomly selected windows of 100 Kb.
This finding suggests that if the initial detector window (1 second) is not matched to length of the repeat (in this case, 850 msec), then a false-negative result can be produced.
