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Updated: Jun 13, 2026
09:24
Preparation of Meiotic Chromosome Spreads from Mouse Oocytes for Assessment of Synapsis and Recombination
Published on: July 18, 2025
Incomplete synapsis and chiasma localization: the chicken or the egg?
A Viera1, J L Santos, M T Parra
1Departamento de Biología, Edificio de Biológicas, Universidad Autónoma de Madrid, ES-28049 Madrid, Spain.
Cytogenetic and Genome Research
|April 15, 2010
Summary
This study on grasshopper species reveals that recombination initiation occurs before synapsis. The research highlights a link between absent meiotic recombination and unsynapsed chromosomal regions during prophase I.
Area of Science:
- Cytogenetics
- Molecular Biology
- Genetics
Background:
- Meiotic recombination is crucial for proper chromosome segregation.
- Synapsis, the pairing of homologous chromosomes, is a key event in meiosis.
- Understanding the interplay between synapsis, recombination, and chromosomal structure is vital in cytogenetics.
Purpose of the Study:
- To compare synaptic patterns in three grasshopper species.
- To analyze the relationship between cohesin axis morphogenesis, double-strand break (DSB) formation, and recombination initiation.
- To investigate the mechanisms behind incomplete synapsis and chiasma localization.
Main Methods:
- Comparative analysis of three grasshopper species with distinct synaptic patterns.
- Detailed examination of cohesin axis morphogenesis.
- Assessment of double-strand break (DSB) formation and recombination initiation during prophase I.
Main Results:
- Recombination initiation consistently precedes synapsis across all studied species.
- A direct correlation exists between the absence of meiotic recombination and the presence of unsynapsed chromosomal regions.
- Specific patterns of synapsis influence recombination outcomes.
Conclusions:
- Proposes mechanisms for incomplete synapsis and chiasma localization in wild species.
- Recombination initiation is an early event, independent of complete synapsis.
- Unsynapsed regions are associated with a lack of meiotic recombination.
Related Concept Videos
01:34Crossing Over
Unlike mitosis, meiosis aims for genetic diversity in its creation of haploid gametes. Dividing germ cells first begin this process in prophase I, where each chromosome—replicated in S phase—is now composed of two sister chromatids (identical copies) joined centrally.
The homologous pairs of sister chromosomes—one from the maternal and one from the paternal genome—then begin to align alongside each other lengthwise, matching corresponding DNA positions in a process called synapsis.
In order to...
The homologous pairs of sister chromosomes—one from the maternal and one from the paternal genome—then begin to align alongside each other lengthwise, matching corresponding DNA positions in a process called synapsis.
In order to...
01:30Crossing Over
Crossing over is the exchange of genetic information between homologous chromosomes during prophase I of meiosis I. Genetic recombination gives rise to allelic diversity in the newly formed daughter cells. In humans, crossing over produces genetically distinct haploid egg and sperm cells that undergo fertilization to produce unique offspring. Before cell division starts, the germ cell’s chromosome(s) undergo duplication in the S phase of the cell cycle. As the cells enter prophase I, duplicated...
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...