gene repeat unit (18-5.8-28S) from Xenopus laevis (Meunier-Rotival
et al., 1979). The probe was labelled with biotin-11-dUTP (Thermo
Scientific) for 1 h 30 min at 15 ◦C using the Nick translation system
(Invitrogen) in accordance with the manufacturer’s instructions.
Hybridisation on interphase nuclei and chromosome spreads was
performed to check proper probe functioning.