Alterations induced in mouse chromosomes by restriction endonucleases

Fixed chromosomes of mouse have been treated with Alu I, Eco RII, Hind III or Bam HI restriction endonucleases and subsequently stained with either Giemsa, Ethidium Bromide or Acridine Orange. The results obtained have been discussed in the light of preferential or non-preferential extraction of DNA from specific chromosome areas following enzyme digestion. The possible involvement of a particular structural organization of some classes of heterochromatin has been hypothesized to account for the findings after Alu I or Eco RII treatment. The meaning of the Giemsa banding observed after Hind III or Bam HI digestion has also been considered, in comparison to the different stain responses obtained by using a DNA-specific dye such as Ethidium Bromide.