Isolation of a new germ line-specific repetitive DNA family in Acricotopus by microdissection of polytenized germ line-limited chromosome sections from a permanent larval salivary gland preparation.

In Acricotopus lucidus (Diptera, Chironomidae) the germ line-limited chromosomes (Ks) have developed from the soma chromosomes (Ss) by endoreduplication, rearrangements and accumulation of germ line-specific repetitive sequences. For molecular analysis of specific small K sections, microdissection of metaphase Ks generally yields very limited amounts of DNA. In this study, K-specific DNA was microdissected from defined polytenized K sections of X-ray induced K-S-rearrangements of permanent salivary gland chromosome preparations and was then amplified by DOP-PCR. A new germ line-specific tandem repetitive DNA family was isolated by this way from a heterochromatic K segment, characterized and localized on the Ks by FISH. The repetitive elements are related to sequences of earlier described K-specific tandem repetitive DNA families in A. lucidus, but are located mainly in terminal heterochromatin bands of the two largest Ks and only to a limited degree in the paracentromeric K heterochromatin. This demonstrates that a collection of permanent preparations of K-S-rearrangements with polytenized heterochromatic and S-homologous K sections of A. lucidus can be used as a source for obtaining K sequences of defined K parts to investigate the molecular evolution of the Ks. Copyright 2002 S. Karger AG, Basel