double signal in chromos. FISH ?

[Carsten Hohoff]

Dear experts in the field of chromosomal FISHing !

I expected a double-signal on metaphase chromosomes (due to the occurrence
of the gene on both chromatides) - but what I observe in nearly half of the
chromosomes inspected is that there is just ONE fluorescence signal !

What imay be the reason ? Is the chromatide DNA not denatured well enough ?

Any helpful comment is appreciated 

Carsten Hohoff