ABSTRACT
Molecular cytogenetics, particularly fluorescence in situ hybridization (FISH), can be applied as one of nowadays three major approaches to study the nuclear architecture; the two other ways to access this problem are based on life-cell imaging, and long read sequencing. According to data obtained during the last decades, in the interphase nucleus the DNA is protein-covered, and there is never-ending transcription, de- and refolding, and repair going on. Besides, chromosomes are arranged in a nucleus normally according to size and gene-density; an exception has yet been seen only in rod cells in retina of nocturnal mammals, where an “inverted” arrangement is needed to support night vision. The mechanical strength of planar chromatin protects the genome integrity, even when double-strand breaks are produced. It is also proposed that multilayer chromatin has two states: inactive when layers are stacked and active when layers are unstacked.
