Replication forks initiate within the telomere repeats in chromosome 10q in a HeLa cell line with long telomeres. SMARD analysis of the Ch10q telomere segment in HeLa 1.3, a line with a mean telomere length of 23 kb, more than twice as long as in most human cells (Takai et al., 2010). Based on the length of the signals for the FISH probes, we estimate that the mean length of the telomeres in Ch10q is ∼40 kb. Telomeric initiation events are detected in molecules containing terminations where the red tract of the 3′-to-5′ fork does not extend out of the telomere or extends only a few kilobases out from the telomere (molecules 1–4). The centers of telomeric initiation events are indicated by yellow asterisks. A termination zone, seen as a valley in the replication profile histogram centered ∼60 kb from the telomere/subtelomere border, indicates the frequent use of two origins separated by at least 120 kb, which fire at similar times to replicate the segment. The yellow arrows indicate the direction of replication fork progression, and the vertical orange and blue lines demarcate the boundaries of sequences where fish probes bind, as described in the legend to Fig. 2.