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Related Concept Videos

Oogenesis01:22

Oogenesis

Oogenesis,  the process of developing egg cells (female gametes), occurs within the ovaries and is fundamental to female fertility. This sequence begins during fetal development when diploid oogonia in the developing ovaries undergo mitotic divisions to produce primary oocytes. By birth, these primary oocytes enter prophase I of meiosis but become arrested in this stage, remaining suspended until puberty.
Each primary oocyte is surrounded by a layer of pre-granulosa cells, forming what is known...
Oogenesis02:07

Oogenesis

In human women, oogenesis produces one mature egg cell or ovum for every precursor cell that enters meiosis. This process differs in two unique ways from the equivalent procedure of spermatogenesis in males. First, meiotic divisions during oogenesis are asymmetric, meaning that a large oocyte (containing most of the cytoplasm) and minor polar body are produced as a result of meiosis I, and again following meiosis II. Since only oocytes will go on to form embryos if fertilized, this unequal...
Meiosis II02:02

Meiosis II

Meiosis II entails cell division and segregation of the sister chromatids, resulting in the production of four unique haploid gametes. The steps for meiosis II are similar to mitosis, except that meiosis II occurs in haploid cells, whereas mitosis occurs in diploid cells.
The timing and cell division patterns of meiosis differ between males and females. In male meiosis, the centrosomes are part of the formation of the meiotic spindle. However, in oocytes, including that of humans, Drosophila,...
Meiosis II01:57

Meiosis II

Meiosis II is the second and final stage of meiosis. It relies on the haploid cells produced during meiosis I, each of which contain only 23 chromosomes—one from each homologous initial pair. Importantly, each chromosome in these cells is composed of two joined copies, and when these cells enter meiosis II, the goal is to separate such sister chromatids using the same microtubule-based network employed in other division processes. The result of meiosis II is two haploid cells, each containing...
The Cell Cycle Control System01:28

The Cell Cycle Control System

The cell cycle regulation directs how a cell proceeds from one phase to the next and begins mitosis. The cell cycle control system includes intracellular regulatory molecules and external triggers. They provide "stop" or "advance" signals and operate at specific cell cycle stages termed checkpoints to ensure that a particular process is completed before the cell advances to the next phase.
Cyclins and cyclin-dependent kinases (Cdks) are the primary cell cycle regulators and function at the cell...
The Spindle Assembly Checkpoint02:19

The Spindle Assembly Checkpoint

The spindle assembly checkpoint is a molecular surveillance mechanism ensuring the fidelity of chromosome segregation during anaphase. The checkpoint monitors the completion of all the prerequisite steps before chromosome segregation to determine whether the segregation process should proceed or be delayed.
Many proteins function together to control the spindle assembly checkpoint. Mutations affecting these proteins may allow cells to proceed into anaphase prematurely, resulting in the...

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A Neural Network-Based Identification of Developmentally Competent or Incompetent Mouse Fully-Grown Oocytes
10:04

A Neural Network-Based Identification of Developmentally Competent or Incompetent Mouse Fully-Grown Oocytes

Published on: March 3, 2018

Mammalian oocyte development: checkpoints for competence.

Trudee Fair1

  • 1Veterinary Sciences Centre and Lyons Research Farm, School of Agriculture, Food Science and Veterinary Medicine, University College Dublin, Belfield, Dublin 4, Ireland. trudee.fair@ucd.ie

Reproduction, Fertility, and Development
|December 17, 2009
PubMed
Summary
This summary is machine-generated.

Female ovarian oocyte development involves critical checkpoints. The secondary follicle stage and periovulatory period are key phases sensitive to environmental factors impacting embryo development.

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Last Updated: Jun 17, 2026

A Neural Network-Based Identification of Developmentally Competent or Incompetent Mouse Fully-Grown Oocytes
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Chromatin Spread Preparations for the Analysis of Mouse Oocyte Progression from Prophase to Metaphase II

Published on: February 26, 2018

Area of Science:

  • Reproductive biology and developmental science.

Background:

  • Biochemical changes in the female ovarian environment influence oocyte quality and embryo development.
  • Endogenous and exogenous factors, including husbandry, production demands, and disease, affect ovarian function.
  • Critical checkpoints in oocyte development remain poorly defined, hindering understanding of developmental sensitivity.

Purpose of the Study:

  • To review key molecular and morphological events during oocyte and follicle growth.
  • To identify critical checkpoints in oocyte development that are particularly sensitive to insult.
  • To elucidate the impact of various factors on female reproductive potential.

Main Methods:

  • Review of existing scientific literature on oocyte and follicle development.
  • Analysis of molecular and morphological events during follicular growth.
  • Identification of key developmental stages and their sensitivities.

Main Results:

  • The secondary follicle stage is a critical checkpoint, characterized by oocyte transcriptome activation, zona pellucida sequestration, granulosa cell-oocyte communication, and cortical granule synthesis.
  • The periovulatory period is another critical checkpoint, involving mRNA transcript regulation, meiosis resumption, spindle formation, and chromosome segregation.
  • These stages represent key periods of vulnerability to factors affecting oocyte quality.

Conclusions:

  • The secondary follicle stage and periovulatory period are identified as crucial checkpoints in female oocyte development.
  • Understanding these critical periods is essential for improving oocyte quality and subsequent embryo development.
  • Further research into factors affecting these checkpoints can enhance reproductive outcomes.