Livingston, Dennis M - CAG tract instability in yeast. CAG tract instability in yeast. D. Livingston, D. Maurer, and B. O'Callaghan. Examination of chromosomal DNA from sibling colonies arising from clonal expansion of strains harboring repeat tracts showed that repeat tracts often change in length. Most changes are decreases in tract length, but rare increases in tract length also occur.
Longer tracts are more unstable than smaller tracts.
The orientation of repeat tracts with respect to the presence of CAG or its complement CTG in the ADE2 clone has a profound effect on its stability. When CAG is in the ADE2 coding strand the repeat tract is relatively stable, and small expansions are the most common change. When CTG is in the ADE2 coding strand the repeat tract is relatively unstable, and long contractions are much more prevalent than expansions.