spindle fibers Spindle fiber - IdmcrackfreedownloadInfo

spindle fibers Spindle fiber

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Spindle fiber

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Definition

noun, plural: spindle fibers

Any of a network of filaments that collectively form a mitotic spindle (in mitosis ) and meiotic spindle (in meiosis ) and responsible in moving and segregating the chromosomes during nuclear division

Supplement

Spindle fibers are filaments that form the mitotic spindle in cell division, i.e. mitosis and meiosis. They are chiefly involved in moving and segregating the chromosomes during nuclear division.

Spindle fibers are made up of microtubules. Microtubules are polymers of alpha- and beta- tubulin dimers . Microtubules that form the spindle fibers come from centrosomes , which are organelles located in opposite poles near the nucleus .

In mitosis , these filaments form at opposite poles of the cell and meet at the equatorial plane . Collectively, they form a spindle-shaped structure, which is widest at the middle then tapers at both ends. The spindle fibers form during prophase . During metaphase of cell division , the spindle fibers radiate from the centrioles at the opposite poles. Some of them attach to the kinetochores of the chromosomes while others bind to the arms of the chromosomes , still others continue to grow. When the spindle fibers start to pull the chromosomes (via their kinetochores ) to opposite poles, this marks the anaphase of cell division .

Variant: spindle fibre

See also:

  • cell division
  • mitosis
  • meiosis
  • prophase
  • metaphase plate
  • kinetochore
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Spindle Fibers: Definition and Function

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Spindle Fibers: Definition and Function




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Spindle Fibers Mitosis




This is a fluorescence micrograph of a cell during metaphase of mitosis. At metaphase, the chromosomes (green) line up along the center of the cell, and the spindle fibers (purple) grow from their poles to the centromeres (yellow), at the center of each chromosome.
Credit: DR PAUL ANDREWS, UNIVERSITY OF DUNDEE/Science Photo Library/Getty Images
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by
Regina Bailey



Regina Bailey is a science writer and educator who has covered biology for ThoughtCo since 1997. Her writing is featured in Kaplan AP Biology 2016.

Updated October 12, 2018

Spindle fibers are aggregates of microtubules that move chromosomes during cell division. Microtubules are protein filaments that resemble hollow rods. They are found in eukaryotic cells and are a component of the cytoskeleton , cilia, and flagella . Spindle fibers are a part of the spindle apparatus, which moves chromosomes during mitosis and meiosis to ensure that each daughter cell gets the correct number of chromosomes. The spindle apparatus consists of spindle fibers, motor proteins, chromosomes, and, in some cells, structures called asters . In animal cells , spindle fibers are produced from cylindrical microtubules called centrioles . Centrioles form asters and asters generate spindle fibers during the cell cycle . Centrioles are located in a region of the cell known as the centrosome.

Spindle Fibers and Chromosome Movement

Spindle fiber and cell movement is the result of interactions between microtubules and motor proteins. Motor proteins are specialized proteins, powered by ATP, that actively move microtubules. Some motor proteins, such as dyneins and kinesins, move along microtubules as the fibers either lengthen or shorten. It is the disassembly and reassembly of microtubules that produces the movement needed for cell division to occur. This includes chromosome movement as well as cytokinesis (the division of the cytoplasm at the end of mitosis or meiosis).

Spindle fibers move chromosomes during cell division by attaching to chromosome arms and chromosome centromeres . A centromere is a specific region of a chromosome where duplicated chromosomes are joined. The identical, joined copies of a single chromosome are known as sister chromatids . The centromere is also where specialized  protein complexes called kinetochores are found. Kinetochores generate kinetochore fibers, which attach sister chromatids to spindle fibers. Kinetochore fibers and spindle polar fibers work together to manipulate and separate chromosomes during mitosis and meiosis. Spindle fibers that don’t contact chromosomes during cell division extend from one cell pole to the other. These fibers overlap and push cell poles away from one another in preparation for cytokinesis.

Spindle Fibers in Mitosis

During prophase of mitosis, spindle fibers form at opposite poles of the cell . In animal cells , the mitotic spindle initially appears as asters, which surround each centriole pair. The cell becomes elongated as spindle fibers extend from each cell pole. Sister chromatids attach to spindle fibers at their kinetochores.

During metaphase , spindle fibers called polar fibers extend from the cell poles toward the midpoint of the cell, which is known as the metaphase plate. Chromosomes are held at the metaphase plate by the force of the spindle fibers pushing on the centromeres of the chromosomes.

In anaphase , spindle fibers shorten and pull  sister chromatids toward the spindle poles. Sister chromatids separate and move toward opposite cell poles. Spindle fibers not connected to chromatids lengthen and elongate the cell.

In telophase , the spindle fibers disperse as the chromosomes are separated and become housed within distinct new nuclei .

At the end of mitosis and cytokinesis, two daughter cells are formed, each with the correct number of chromosomes. In human cells, there are 23 pairs of chromosomes, for a total of 46. Spindle fibers function similarly in meiosis , where four daughter cells are formed instead of two.


  • Asters in Mitosis

    What Are Asters?

  • Chromosomes

    How Does a Centromere Aid in Chromosome Separation?

  • Kinetochore

    How Kinetochores Help Split Cells

  • Cancer Cell Mitosis

    What Are Daughter Cells?

  • Centrioles

    The Role Centrioles Play in Cell Division

  • A plant cell in Interphase

    Discover What Occurs During the Different Stages of Meiosis

  • Illustration depicting the stages of mitosis and cell divison

    The Stages of Mitosis and Cell Division

  • Fibroblast cells showing cytoskeleton

    Microtubules: The Scaffolding of Cells

  • Microscope image of plant cells with three nuclei in anaphase

    Learn the Language of Mitosis

  • Dividing Cell

    Glossary of Cell Biology Terms from Anaphase to Telophase

  • Chromatin and DNA Compaction

    What Is Chromatin?

  • Nuclear Chromosome

    Chromosomes: The Gene Carriers of a Cell

  • Sister Chromatids

    What Are Sister Chromatids?

  • Meiosis Anaphase I

    What Is Anaphase in Cell Biology?

  • Chromosomes

    What Is a Chromatid?

  • Plant Mitosis - Anaphase

    What Is a Daughter Chromosome?







Dictionary.com

spindle fiber

n.
  1. One of a network of achromatic filaments that extend inward from the poles of a dividing cell, forming a spindle-shaped figure.
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The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

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Nearby words for spindle fiber


  1. spinate
  2. spindle
  3. spindle cell
  4. spindle cell carcinoma
  5. spindle cell lipoma
  6. spindle fiber
  7. spindle file
  8. spindle side
  9. spindle tree
  10. spindle-legged
  11. spindleage

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