Representative STELA blot. DNA extracted from sorted subpopulations of cells was taken through STELA PCR to amplify XpYp telomeres. An estimated concentration of 50 amplifiable molecules was added to each master mix, and aliquoted into 5 separate PCR tubes to ensure clear identification of resolved products. Amplicons were resolved on 0.7% agarose, Southern blotted, and detected with an XpYp-specific probe. Each amplicon represents the product from a single telomere end from a single cell, allowing telomere measurements of highly limiting cell populations. Amplicons were binned into size windows to determine mean telomere lengths, and products falling outside 1.4826 MAD from the median were counted and classified as ultrashort “outlier” telomeres.