1. the nuclei of male and female gametes before they fuse during fertilization
Usage: biology; plural of pronucleus

Examples

• The sperm and egg pronuclei move toward each other after fertilization begins.
• Scientists observed the pronuclei under a microscope during the embryology experiment.
• The fusion of pronuclei marks the completion of fertilization in mammals.
• Each pronucleus contains half the genetic material needed for development.
• Researchers studied the timing of pronuclei formation in different species.
• The pronuclei remain separate for several hours before combining their chromosomes.