TERC directs the sequential addition of nucleotides to the 3' end of a chromosomal DNA strand with one added telomere repeat. After each addition, the template must move relative to the telomerase active site to bring the next template residue into the active site. The product of these additions and translocations is a chromosomal single-stranded end extended by two repeat units (each complementary to the TERC template sequence), positioned on the template so as to allow repetition of the process. The template region of TERC is perfectly conserved between humans and chickens (Chen et al. 2000). The molecular details of the process have been studied in humans; the orthologous chicken event is inferred from those data.