INSITU NICK TRANSLATION OF MEIOTIC CHROMOSOMES TO DEMONSTRATE HOMOLOGOUS HETEROCHROMATIN HETEROGENEITY

The in situ nick translation procedure performed on fixed meiotic chro mosomes partially cleaved with restriction endonucleases shows a diffe rent staining of homologous heterochromatic regions, which could be ex plained through a differential restriction endonuclease cleavage. Muta tions occurring before massive tandem duplication and involving those DNA motifs that produce these heterochromatic blocks, together with th e absence of DNA recombination that characterizes these particular reg ions, could explain the observed results. This method for chromosome l abelling is most useful to demonstrate a certain level of heterochroma tin heterogeneity that is present in the genome of living species but remained cryptic to other techniques that are also able to induce long itudinal differentiation of the chromosomes.