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Related Concept Videos

Crossing Over01:30

Crossing Over

7.1K
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,...
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Crossing Over01:34

Crossing Over

173.9K
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...
173.9K
Crossing over01:34

Crossing over

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No description available
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Gene Conversion02:08

Gene Conversion

10.8K
Other than maintaining genome stability via DNA repair, homologous recombination plays an important role in diversifying the genome. In fact, the recombination of sequences forms the molecular basis of genomic evolution. Random and non-random permutations of genomic sequences create a library of new amalgamated sequences. These newly formed genomes can determine the fitness and survival of cells. In bacteria, homologous and non-homologous types of recombination lead to the evolution of new...
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Homologous Recombination02:31

Homologous Recombination

65.1K
The basic reaction of homologous recombination (HR) involves two chromatids that contain DNA sequences sharing a significant stretch of identity. One of these sequences uses a strand from another as a template to synthesize DNA in an enzyme-catalyzed reaction. The final product is a novel amalgamation of the two substrates. To ensure an accurate recombination of sequences, HR is restricted to the S and G2 phases of the cell cycle. At these stages, the DNA has been replicated already and the...
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Homologous Recombination02:31

Homologous Recombination

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No description available
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Related Experiment Video

Updated: Mar 20, 2026

Preparation of Meiotic Chromosome Spreads from Mouse Oocytes for Assessment of Synapsis and Recombination
09:24

Preparation of Meiotic Chromosome Spreads from Mouse Oocytes for Assessment of Synapsis and Recombination

Published on: July 18, 2025

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The synaptinemal complex and four-strand crossing over.

D von Wettstein

    Proceedings of the National Academy of Sciences of the United States of America
    |April 1, 1971
    PubMed
    Summary

    The synaptinemal complex structures chromosome crossover. It forms from sister chromatids before pairing, then combines into a single complex per bivalent during precise homologous chromosome pairing.

    Area of Science:

    • Genetics
    • Molecular Biology
    • Cell Biology

    Background:

    • The synaptinemal complex is crucial for homologous chromosome pairing and genetic recombination during meiosis.
    • Understanding its structural formation is key to deciphering the mechanisms of crossover.
    • Previous models lacked a clear explanation for the involvement of sister chromatids in initial complex assembly.

    Purpose of the Study:

    • To elucidate the structural basis of four-strand crossing over mediated by the synaptinemal complex.
    • To detail the process of synaptinemal complex formation from sister chromatids and homologous chromosomes.

    Main Methods:

    • The study likely involved advanced microscopy techniques and biochemical analyses to visualize and characterize the synaptinemal complex.
    • Detailed observation of chromosome pairing and synaptinemal complex assembly at the molecular level.

    More Related Videos

    Frequency and Distribution of Crossovers in Caenorhabditis elegans Meiosis by SNP Genotyping using Real-time PCR
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    Frequency and Distribution of Crossovers in Caenorhabditis elegans Meiosis by SNP Genotyping using Real-time PCR

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    Super-Resolution Microscopy of the Synaptonemal Complex Within the Caenorhabditis elegans Germline
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    Super-Resolution Microscopy of the Synaptonemal Complex Within the Caenorhabditis elegans Germline

    Published on: September 13, 2022

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    Related Experiment Videos

    Last Updated: Mar 20, 2026

    Preparation of Meiotic Chromosome Spreads from Mouse Oocytes for Assessment of Synapsis and Recombination
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    Frequency and Distribution of Crossovers in Caenorhabditis elegans Meiosis by SNP Genotyping using Real-time PCR
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    Frequency and Distribution of Crossovers in Caenorhabditis elegans Meiosis by SNP Genotyping using Real-time PCR

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    Super-Resolution Microscopy of the Synaptonemal Complex Within the Caenorhabditis elegans Germline
    09:14

    Super-Resolution Microscopy of the Synaptonemal Complex Within the Caenorhabditis elegans Germline

    Published on: September 13, 2022

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    Main Results:

    • The synaptinemal (SC) complex provides a structural foundation for four-strand crossing over.
    • Sister chromatids of each homologous chromosome contribute to forming one lateral component before chromosome pairing.
    • During precise pairing, two lateral components merge to create a single SC per bivalent.

    Conclusions:

    • The synaptinemal complex formation involves a coordinated process utilizing sister chromatids for initial structural components.
    • This mechanism ensures the precise pairing of homologous chromosomes and facilitates genetic exchange through crossover.