An unusual variant chromosome 9 with an extra C-negative, G-dark segment in the short arm.

An unusual variant chromosome 9 is described in a mother and a daughter: an extra G-dark, C-negative and G-11 negative chromosomal segment is present in the short arm in the absence of apparent phenotypic effects. This extra material is also Ag-As negative and exhibits a fluorescence similar in intensity to that of band 9q21 when stained by QFQ and DAPI/AMD, and to that of band 9p13 in RBA-banded preparations; it is slightly less fluorescent when R-banded by chromomycin A3. The possibility of an association with an increased risk of spontaneous abortion is presented.