Related Experiment Video
Updated: Jun 4, 2026
10:39
Chromatin Spread Preparations for the Analysis of Mouse Oocyte Progression from Prophase to Metaphase II
Published on: February 26, 2018
Chromosome abnormalities in the human oocyte.
E Fragouli1, D Wells, J D A Delhanty
1Institute of Reproductive Sciences, Nuffield Department of Obstetrics and Gynaecology, University of Oxford, Oxford, UK. elpida.fragouli@obs-gyn.ox.ac.uk
Cytogenetic and Genome Research
|January 29, 2011
Summary
Aneuploidy, a common chromosome abnormality, often results from errors in female meiosis, linked to maternal age. This study examines the mechanisms causing aneuploidy during meiosis using oocyte and polar body analysis.
Area of Science:
- Reproductive biology
- Genetics
- Cell biology
Background:
- Aneuploidy is the most frequent chromosome abnormality with significant clinical implications.
- It is primarily caused by errors during female meiosis, particularly associated with increasing maternal age.
- Two primary mechanisms lead to aneuploidy: chromosome non-disjunction and premature sister chromatid division.
Purpose of the Study:
- To investigate the mechanisms underlying maternally derived aneuploidy.
- To understand how these mechanisms impact the two meiotic divisions in females.
- To explore the relationship between oocyte maturity, maternal age, chromosome status, and meiotic errors.
Main Methods:
- Examination of a large cohort of human oocytes and their corresponding polar bodies.
- Application of classical and molecular cytogenetic techniques for analysis.
- Gene expression profiling of oocytes based on maturity, maternal age, and chromosomal status.
Main Results:
- Cytogenetic and molecular analyses provided valuable data on aneuploidy-causing mechanisms.
- Gene expression studies offered insights into the regulatory pathways of female meiosis.
- Evidence was gathered on the specific contributions of each meiotic division to aneuploidy.
Conclusions:
- The study elucidates the complex mechanisms of female meiotic errors leading to aneuploidy.
- Findings highlight the critical role of maternal age and provide a deeper understanding of oocyte biology.
- This research contributes to comprehending the genetic and biological factors influencing chromosome segregation in oocytes.
Related Concept Videos
02:07Oogenesis
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...
01:22Oogenesis
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...
Each primary oocyte is surrounded by a layer of pre-granulosa cells, forming what is known...
01:29Nondisjunction
During meiosis, chromosomes occasionally separate improperly. This occurs due to failure of homologous chromosome separation during meiosis I or failed sister chromatid separation during meiosis II. In some species, notably plants, nondisjunction can result in an organism with an entire additional set of chromosomes, which is called polyploidy. In humans, nondisjunction can occur during male or female gametogenesis and the resulting gametes possess one too many or one too few chromosomes.
01:21Nondisjunction
Nondisjunction is the failure of homologous chromosomes or sister chromatids to separate correctly and move to the opposite poles of the cells. This produces daughter cells with abnormal chromosome numbers. Nondisjunction is common during anaphase I or anaphase II of meiosis. Mutations in synaptonemal complex proteins that attach homologous chromosomes increase the chances of nondisjunction in anaphase I of meiosis I. In contrast, mutations in topoisomerases and condensins that hold sister...
01:49Meiosis I
Meiosis is a carefully orchestrated set of cell divisions, the goal of which—in humans—is to produce haploid sperm or eggs, each containing half the number of chromosomes present in somatic cells elsewhere in the body. Meiosis I is the first such division, and involves several key steps, among them: condensation of replicated chromosomes in diploid cells; the pairing of homologous chromosomes and their exchange of information; and finally, the separation of homologous chromosomes by a...
03:09Meiosis I
Meiosis is the division of a diploid cell into haploid cells forming sperm and eggs in animals through differentiation. Meiosis I is the first stage of meiosis, where the genetic recombination of homologous chromosomes and the reduction of the ploidy level by half occurs.
Prophase I is the most extended and complex step of meiosis I characterized by synapsis, chromosome pairing, and recombination of the homologous chromosomes. This process is facilitated by a proteinaceous structure called the...
Prophase I is the most extended and complex step of meiosis I characterized by synapsis, chromosome pairing, and recombination of the homologous chromosomes. This process is facilitated by a proteinaceous structure called the...