FIG. 5.

The telomere can align with nucleotides within the core of the template. (A) ter1-28A/30G copies a 20-bp repeat. The telomeric repeats made in the ter1-28A/30G strain are 20 bp long. It is unclear whether position 30 is typically copied in vivo; however, the mutations cause the sequence in TR26-30 to be identical to the sequence at positions 6 to 10 (underlined with arrows). The change potentially templated by position 30 is shown in gray, as is the mutation introduced by position 28 (marked with dots). (B) ter1-28A copies a 20-nt repeat or stutters. Telomeres cloned from a strain containing ter1-28A often contain 20-bp repeats identical to those made in the ter1-28A/30G mutant strain. Sometimes, however, a sequence that is not easily explained was found (shown in gray italics). (C) ter1-27G leads to the synthesis of 13-nt repeats or unusually long repeats. When a G is copied from position 27, the telomeric tip can base pair with positions 13 to 15 of the template, leading to the synthesis of a 13-nt repeat. In other cases, aberrant synthesis occurs (extra sequence shown in gray italics).