pronuclei
Pronunciation: proh-NOO-klee-eye
The paired nuclei visible in a fertilized egg before they fuse, indicating successful fertilization in embryology assessment.
Full Definition
Pronuclei are the two distinct nuclei observed in a fertilized oocyte approximately 16-20 hours after insemination or injection, representing the maternal and paternal genetic contributions before nuclear fusion occurs. The presence of two pronuclei (2PN) confirms normal fertilization and is a critical checkpoint in embryology assessment during assisted reproductive technology procedures. Abnormal fertilization is indicated by the presence of one pronucleus (1PN, parthenogenetic activation) or three or more pronuclei (3PN or more, indicating polyspermy or other fertilization abnormalities). Embryos showing normal 2PN fertilization are selected for further culture and potential transfer, while abnormally fertilized embryos are typically discarded due to chromosomal abnormalities.
Usage
Usage note: Plural of pronucleus; often documented as '2PN' for normal fertilization.
In Context
- "Fertilization assessment revealed normal pronuclei formation in 8 of 12 oocytes." — Embryology report
- "Three embryos showed abnormal pronuclei and were excluded from transfer consideration." — Laboratory assessment