Distribution of TaqI sites along human chromosomes revealed by in situ enzyme-nick translation.

We have studied the relative richness of TaqI sites along human chromosomes by means of a nonradioactive in situ enzyme-nick translation procedure. Regions with a higher content of these sequences are shown to be the noncentromeric heterochromatin blocks, whereas within euchromatin, terminal R-bands are the domains more enriched in these sites. Results obtained suggest that the method of performing enzyme digestions using time as a variable, and then in situ nick translation, provides much more complete information about the distribution of enzyme sequences along chromosomes than standard enzyme digestions.