Shown is an example of a Southern blot telomere length determination for two patients, patient 6 and patient 7, described in the text and tables. Lanes 1 and 13 and 14 are marker lanes, with the sizes of the markers indicated at left. Lanes 3 to 7 show the TRFs from the cells of pediatric patient 6 obtained at the times after birth, indicated at the top of the figure. Lanes 8 to 12 show the TRFs from the cells of pediatric patient 7 obtained at the times indicated at the top of the figure.