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Related Concept Videos

Meiosis II02:02

Meiosis II

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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,...
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Crossing Over01:34

Crossing Over

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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...
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Meiosis I03:09

Meiosis I

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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...
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Conservative Site-specific Recombination and Phase Variation02:53

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Because the DNA segments are cut and reorganized in a direction-specific manner, site-specific recombination has emerged as an efficient genetic engineering technique. Flippase and Cyclization recombinases or Flp and Cre, respectively, are two members of the tyrosine recombinase family derived from bacteriophages, that are used to mediate site-specific DNA insertions, deletions, and targeted expression of proteins in mammalian cell lines.
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Meiosis vs. Mitosis02:57

Meiosis vs. Mitosis

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Cell division is necessary for growth and reproduction in organisms. Mitosis aids cell growth and development by dividing somatic cells. In contrast, meiosis causes the division of germ cells and plays an essential role in sexual reproduction. Due to their unique functional requirements, mitosis and meiosis differ from each other in multiple aspects.
Before the start of mitosis and meiosis I, the cell synthesizes DNA, resulting in two homologous copies of each chromosome. DNA synthesis is...
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Gene Conversion02:08

Gene Conversion

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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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Related Experiment Video

Updated: Aug 28, 2025

Use of Time-Lapse Microscopy and Stage-Specific Nuclear Depletion of Proteins to Study Meiosis in S. cerevisiae
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Use of Time-Lapse Microscopy and Stage-Specific Nuclear Depletion of Proteins to Study Meiosis in S. cerevisiae

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Negative supercoils regulate meiotic crossover patterns in budding yeast.

Taicong Tan1, Yingjin Tan1, Ying Wang1

  • 1Center for Reproductive Medicine, Cheeloo College of Medicine, State Key Laboratory of Microbial Technology, Shandong University, China.

Nucleic Acids Research
|September 15, 2022
PubMed
Summary
This summary is machine-generated.

Negative supercoils regulate meiotic crossovers, crucial for chromosome segregation. Their accumulation and relief, influenced by Top2 activity, dictate crossover interference strength and patterns.

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Area of Science:

  • Genetics
  • Molecular Biology
  • Cell Biology

Background:

  • Crossover interference is a fundamental biological process governing the distribution of meiotic crossovers.
  • Meiotic crossovers are essential for accurate chromosome segregation during meiosis and contribute to genetic diversity.
  • The molecular mechanisms underlying crossover interference, including the nature of the interference signal and its regulation, remain largely unknown.

Purpose of the Study:

  • To investigate the role of DNA supercoiling in regulating crossover interference during meiosis.
  • To determine how Top2 enzyme activity, which affects DNA supercoiling, influences interference patterns.
  • To explore the relationship between negative supercoils, Zip3 localization, and crossover interference.

Main Methods:

  • Utilized yeast top2 mutants with specific defects in DNA binding, cleavage, religation, or release.
  • Assessed crossover interference strength and levels of negative supercoiling in these mutants.
  • Examined the enrichment of negative supercoils and Zip3 in crossover-associated regions before meiotic DNA double-strand breaks.

Main Results:

  • Yeast top2 alleles unable to bind or cleave DNA showed increased negative supercoils and reduced interference.
  • Top2 alleles impaired in religation or release accumulated fewer negative supercoils and exhibited stronger interference.
  • A negative correlation was observed between negative supercoil levels and crossover interference strength.
  • Negative supercoils were found to enrich in Zip3-associated regions prior to double-strand break formation, with higher supercoiling correlating with more Zip3.
  • Crossover interference strength and homeostasis exhibited coordinated changes in mutants.

Conclusions:

  • The accumulation and relief of negative supercoils play a critical role in patterning meiotic crossovers.
  • Top2-mediated regulation of DNA supercoiling is a key mechanism controlling crossover interference.
  • Negative supercoils may act as a signal or influence the establishment of crossover interference patterns.