Figure 9.13: Telomeres and Telomerase (A) In most cells, the chromosome shortens with each replication because the nonreplicated DNA at the 3′ end of the template DNA is removed. However, in stems cells, gamete-forming cells, and cancer cells, telomerase uses an RNA template to extend the telomere and prevent chromosome shortening. (B) Bright yellow fluorescent staining marks the telomeric regions on these blue-stained human chromosomes. (C) Analogous to chromosomes without telomeres, shoelaces without tips lose their integrity.