Definition

1. Noun:
   • The nucleus of a sperm or an egg cell during the process of fertilization, before they merge: A "pronucleus" is the haploid nucleus of a male or female gamete (sperm or ovum) present in the fertilized egg immediately after fertilization. It exists as a distinct structure before it fuses with the other pronucleus to form the diploid nucleus of the zygote.

Usage Examples

• Noun:
  • The male and female pronuclei are visible under the microscope shortly after fertilization.
  • In vitro fertilization techniques allow scientists to observe the formation of the pronucleus.
  • The migration and apposition of the two pronuclei is a critical step in early embryonic development.

Advanced Usage

• "Pronuclear stage": Refers to the specific phase in embryonic development immediately following fertilization when the pronuclei are present but have not yet fused.
  • The embryo at the pronuclear stage is assessed for quality before transfer.

Variants and Related Words

• Pronuclei (n): The plural form of "pronucleus."

  • The two pronuclei fuse to complete the process of syngamy.

• Pronuclear (adj): Relating to or characteristic of a pronucleus.

  • Pronuclear transfer is a technique used in mitochondrial replacement therapy.

Synonyms

• Gamete nucleus: The nucleus of a reproductive cell (sperm or egg).
• Haploid nucleus: A nucleus containing a single set of unpaired chromosomes, characteristic of a gamete.

Notes on Meaning

• The term "pronucleus" is specifically used in the context of cytology and embryology. It denotes a transient, intermediate structure in the life cycle of a cell, existing only between fertilization and the first mitotic division of the zygote. It is not a general term for any cell nucleus.

Noun

1. the nucleus of the ovum or sperm after fertilization but before they fuse to form the nucleus of the zygote