CHARACTERIZATION OF THE HETEROCHROMATIN OF THE DARKLING BEETLE MISOLAMPUS-GOUDOTI - CLONING OF 2 SATELLITE DNA FAMILIES AND DIGESTION OF CHROMOSOMES WITH RESTRICTION ENZYMES

The darkling beetle Misolampus goudoti Er. has 58 % of C-banded chromo some material. In this paper we deal with the study of the heterochrom atin of this insect both by molecular and cytogenetical methods. Two d ifferent satellite DNA families have been characterized in Misolampus goudoti by agarose gel electrophoresis of EcoRI and PstI restriction f ragments, respectively. The EcoRI family is composed of a monomeric un it of 196 bp (64.3 % A-T rich) DNA sequence, representing about 120,00 0 copies per haploid genome. The presence of frequent intermediate-siz e satellite variants and an internal direct repetition of 61 bp in the EcoRI repetitive main monomer suggest that the evolution of this sate llite proceeded by unequal crossing-over, occurring both within and be tween the 196 bp unit. Another highly repetitive sequence, defined by digestion of genomic DNA with PstI, has a more complex unit of 1.2 kb with about 70,000 copies per haploid genome. In situ digestion of M. g oudoti chromosomes with restriction enzymes shows a non-specific chrom osome DNA extraction from pericentromeric positions with EcoRI and chr omosome specific extraction of DNA with PstI and HinfI. This is discus sed in relation to the chromosomal location of both satellites.