Figure 3.

The 3′ terminus of yeast telomeres has an irregular sequence. The last 20 nt of telomere sequence are shown. The total length of the TG_1–3 tract recovered is indicated in parentheses. No preference for a guanine or thymine base at the 3′ position is evident (left, seven representative telomeres are shown). This heterogeneity is also present at telomeres isolated from yeast cells lacking telomerase RNA (centre, the telomeres shown were recovered at the point of senescence). Deletion of the yeast Ku70 subunit (yku70-Δ) does not affect the variability of the telomeric end (right). The sequenced telomeres of all strains contained some non-consensus adenine and cytosine bases (e.g. centre). They are stably maintained in the centromere-proximal part (see also Fig. 4C) and therefore not introduced during PCR amplification.