Related Experiment Video
Updated: Oct 19, 2025

Zygotic Fluorescence Recovery After Photo-bleaching Analysis for Chromatin Looseness That Allows Full-term Development
Published on: June 12, 2018
Developmental trajectory of monopronucleated zygotes after in vitro fertilization when they include both male and
Xingqiang Wei1, Noritoshi Enatsu2, Kohyu Furuhashi2
1Graduate School of Environmental and Life Science, Okayama University, Okayama, Japan; Hanabusa Women's Clinic, Kobe, Japan.
Objective:
To examine the cause of monopronucleated zygote (1PN) formation that includes both maternal and paternal genomes.
Design:
Retrospective cohort study.
Setting:
Private fertility clinic.
Patient(S):
A total of 44 1PN and 726 2-pronuclear zygotes from 702 patients were observed using 2 different time-lapse observation systems.
Intervention(S):
Previously recorded time lapse data were reviewed to examine the mechanism of 1PN formation.
Main Outcome Measure(S):
The distance between the position of the second polar body extrusion and the fertilization cone or epicenter/starting position of the cytoplasmic wave was measured, and the consequent data were analyzed. Cytoplasmic waves were confirmed using vector analysis software.
Result(S):
The cut-off value for the difference in the distance between the position of the second polar body extrusion and the fertilization cone or the epicenter/starting position of the cytoplasmic wave was 17 μm (AUC: 0.987, 95% CI: 0.976-0.999) for the Embryo Scope and 18 μm (AUC: 0.972, 95% CI: 0.955-0.988) for the iBIS time-lapse observation systems.
Conclusion(S):
In this study, it was found with a high degree of accuracy that a monopronucleus is formed when the fusion of the sperm takes place within 18 μm from the point of the second polar body extrusion. The theoretical chance of 1PN occurrence after in vitro fertilization is 2.7% when the sperm is considered to be fused anywhere in the plasma membrane of an oocyte.
Related Concept Videos
Fertilization
Cleavage and Blastulation
Meiosis I
The Y Chromosome Determines Maleness
Evolution
Around 300 million years ago, the two sex chromosomes diverged from two identical autosomal chromosomes. Over time, the Y chromosome has lost most of its genes, shrinking in size....
Development of the Sexual Organs in the Embryo and Fetus
Near the gonadal ridges, two duct systems are present: the mesonephric ducts (Wolffian ducts) and paramesonephric ducts (Müllerian ducts). These ducts form the basis for the...
Nondisjunction

