ABSTRACT
Figure 4.2 Fluorescence in situ hybridization (FISH) images of first polar body (PB1) and second polar body (PB2) after a 3-h hybridization with MultiVysion PB panel probe for autosomes 13 (red), 16 (aqua), 18 (violet blue), 21 (green), and 22 (gold). PB1 and PB2 were removed simultaneously on day 1 at the pronuclear stage of development following fertilization assessment. (a) PB1 chromosomes showing a normal number of single dot signals (two per chromosome, representing each chromatid) in which all chromatids are separate. This chromatid separation allows for easy enumeration of chromatids, enabling identification of not only chromosome non-disjunction, but also chromatid errors found to be more prevalent. A normal number of signals (one per chromosome (chromatid)) are present in the PB2 interphase nucleus (lower right), implying a normal chromosome complement in the oocyte and resulting embryo. (b) FISH image of PB1 in which a normal number of signals are seen. Some chromatids are in closer proximity to one another (e.g. chromatids for chromosome 21 in green). Centromeric enumeration signals for chromosome 16 (16q11.2) in aqua appear equally large and diffuse and can vary depending upon the degree of chromatin condensation, since the probe targets a region of highly repetitive satellite DNA sequences. The PB2 nucleus contains a normal number of signals for the five autosomes tested. (c) FISH image of PB1 in which a normal number of signals are seen, with all chromatids being separate and easily counted, except signals for chromosome 16 (white arrows), which once again are diffuse, with one in particular being split, necessitating re-hybridization using a probe that targets the same chromosome but at a different locus. The PB2 nucleus contains a normal number of signals for each of the autosomes tested. (d) FISH image of PB1 in which a normal number of signals are seen. The chromatids are seen paired with a slight overlap for chromosomes 13 (red arrows) and 21 (green arrows). The PB2 nucleus contains a normal number of signals for each of the autosomes tested.
