Fig. 1.

Scheme of a chromosome bearing two telomeres and undergoing replication. Telomeres end with a 3′ overhang of length a (measured to be 5–10 nucleotides in yeast (Soudet et al., 2014), chosen here as a=1 or 7 for theoretical or numerical purposes, respectively). After DNA replication, each telomere generates, through either the leading or the lagging strand replication machineries, two new telomeres of different lengths. The coupling effect between the two ends of the same chromosome imposes that only one of the two is shortened while the other retains the parental length.