The tendency for differences in repeat length to occur in the form of insertions and deletions of whole repeated units increases with repeat tract length.

<p>The percent in-phase values of uninterrupted 2mer, 3mer, 4mer, and 5mer repeats approached a plateau at repeat lengths of 13, 20, 23, and 27 bases respectively, where length-changes are close to 100% in-phase. Genotypes for pure repeats were determined in all the DGRP lines if there were at least two scorable reads and a read was scored if it spanned the repeat region with 3 or more matching flank bases on either side of the repeat.