OBJECTIVE: The purpose of this study was to search for cytologic evidence of 
robertsonian translocation formation that involves chromosomes 14q and 21q in 
human oogenesis with the use of dual color fluorescent in situ hybridization 
with whole chromosome paints.
STUDY DESIGN: The oocytes from a chromosomally normal fetus at 23.5 weeks of 
gestation underwent cohybridization with chromosome specific DNA libraries from 
chromosomes 14 and 21. The nuclei were scored for the proportion of meiosis I 
prophase substages and for hybridization efficiency and were evaluated for the 
presence of hybridization signals that were suggestive of heterologous 
associations between chromosomes 14q and 21q in zygotene, pachytene, and 
diplotene.
RESULTS: A total of 1769 meiotic nuclei were analyzed. Of 272 informative nuclei 
at zygotene, pachytene, and diplotene, 1 nucleus at pachytene demonstrated 
hybridization signals for chromosomes 14 and 21 that could be consistent with a 
robertsonian translocation.
CONCLUSION: A heterologous association between chromosomes 14q and 21q that 
possibly represent robertsonian translocation formation was observed 
cytologically with the use of fluorescent in situ hybridization.