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Related Concept Videos

The Spindle Assembly Checkpoint02:19

The Spindle Assembly Checkpoint

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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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The Mitotic Spindle02:27

The Mitotic Spindle

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The mitotic spindle—or spindle apparatus—is a eukaryotic, cytoskeletal structure made up of long protein fibers called microtubules. Formed during cell division, the spindle separates sister chromatids and moves them to opposite ends of a parental cell, where the now individual chromosomes are distributed to two daughter cell nuclei.
The bipolar configuration of the mitotic spindle facilitates chromosomal segregation, preparing the cell for division. One mechanism that ensures...
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Forces Acting on Chromosomes02:11

Forces Acting on Chromosomes

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During mitosis, chromosome movements occur through the interplay of multiple piconewton level forces. In prometaphase, these forces help in chromosome assembly or congression at the equatorial plane, eventually leading to their alignment at the metaphase plate. The forces acting on the chromosomes are space and time-dependent; therefore, they vary with the position of the chromosomes as the cell progresses through mitosis. 
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Attachment of Sister Chromatids02:57

Attachment of Sister Chromatids

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As cells progress into mitosis, the nuclear envelope breaks down, and the condensed chromosomes are exposed to the array of bipolar microtubules of the mitotic spindle. The kinetochore, a large, disc-shaped protein complex, is present at the centromere region of the sister chromatids and acts as a binding site for the microtubules.  Usually, the plus-end of a single microtubule is embedded within the kinetochore. However, some kinetochores first establish lateral contact with the side-wall...
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Spindle Assembly02:50

Spindle Assembly

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Spindle assembly occurs through three, often coexisting, pathways – the centrosome-mediated pathway, the chromatin-mediated pathway, and the microtubule-mediated pathway – collectively contributing to form a robust spindle apparatus.
In most cells, centrosomes are the primary microtubule nucleation centers. In the centrosome-mediated pathway, the G2-prophase transition triggers centrosome maturation and increased microtubule nucleation. Progressive nucleation results in a...
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Centrioles and Centrosomes01:13

Centrioles and Centrosomes

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Most animal cells comprise a pair of centrioles together called a centrosome. The cell duplicates its centrosome and contains two centrosomes side-by-side, which begin to move apart during the prophase. As the centrosomes migrate to two different sides of the cell, microtubules start extending from each centrosome toward the other end. The mitotic spindle is composed of the centrosomes and their emerging microtubules.
Near the end of the prophase, also called late prophase or...
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Related Experiment Video

Updated: Oct 3, 2025

Reconstitution of Basic Mitotic Spindles in Spherical Emulsion Droplets
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Reconstitution of Basic Mitotic Spindles in Spherical Emulsion Droplets

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Shaping centromeres to resist mitotic spindle forces.

Josh Lawrimore1, Kerry Bloom1

  • 1Department of Biology, 623 Fordham Hall CB#3280 133 Medical Drive, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-3280, USA.

Journal of Cell Science
|February 18, 2022
PubMed
Summary

The centromere acts as a chromatin bottlebrush, organized by cohesin and condensin. This structure creates tension between sister kinetochores, essential for chromosome segregation during cell division.

Keywords:
BottlebrushCentromereKinetochoreMitosisPolymer models

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Immunofluorescence Analysis of Endogenous and Exogenous Centromere-kinetochore Proteins

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Related Experiment Videos

Last Updated: Oct 3, 2025

Reconstitution of Basic Mitotic Spindles in Spherical Emulsion Droplets
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Reconstitution of Basic Mitotic Spindles in Spherical Emulsion Droplets

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Immunofluorescence Analysis of Endogenous and Exogenous Centromere-kinetochore Proteins
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Immunofluorescence Analysis of Endogenous and Exogenous Centromere-kinetochore Proteins

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Live Cell Imaging to Assess the Dynamics of Metaphase Timing and Cell Fate Following Mitotic Spindle Perturbations
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Area of Science:

  • Cell Biology
  • Biophysics
  • Genetics

Background:

  • The centromere is crucial for chromosome segregation, binding the kinetochore.
  • Centromere DNA sequences vary significantly across species.
  • Pericentromeric chromatin structure is key to resisting mechanical forces during mitosis.

Purpose of the Study:

  • To elucidate the physical structure of centromere chromatin.
  • To understand how pericentromeric chromatin forms a tension-generating spring.
  • To propose a model for centromere organization by structural maintenance of chromosome proteins.

Main Methods:

  • Chromatin immunoprecipitation followed by sequencing (ChIP-seq).
  • High-throughput chromosome conformation capture (Hi-C).
  • Quantitative comparison of experimental data with computational simulations.

Main Results:

  • The pericentromere is enriched with cohesin and condensin.
  • A chromatin bottlebrush model is proposed for centromere organization.
  • Steric repulsion between radial loops in the bottlebrush creates spring-like tension.

Conclusions:

  • The chromatin bottlebrush model explains centromere's ability to withstand mechanical stress.
  • Cohesin and condensin are key organizers of this structure.
  • The bottlebrush is a fundamental principle in chromosome organization.