Name: cell division: mitosis and cytokinesis
Uploaded: 2023-06-23T15:38:45.000Z
Duration: 1 min 35 s
Channel: JoVE

有糸分裂は、細胞の遺伝物質が2つの娘細胞間で分割される細胞分裂の一形態です。 
まず、前期には、核クロマチンが凝縮して、セントロメア接合部に付着した姉妹染色分体対からなるX字型の染色体になります。
同時に、中心体は反対側の細胞側に移動します。そうすると、微小管ロッドがそれぞれから成長し始め、ウェブ状の紡錘体装置を形成します。
次に、核膜は前中期に溶解し、動原体と呼ばれるタンパク質構造がセントロメアの両側に現れ、クロマチンごとに1つずつ現れます。
これらの動原体が形成されると、伸びる内部の微小管がそれらに固定され、各姉妹染色分体は異なる細胞極につながれます。
中期では、紡錘体装置は、染色体が細胞の赤道に沿って一定の列に配向するように染色体を再配置します。
後期になると、動原体に固定された微小管が短くなり、姉妹染色分体が引きずられます。これらおよび他の微小管のダイナミクスも細胞を伸長させます。
終期には、紡錘体装置が解散し、染色分体が緩み、核膜が再形成されます。
最後に、細胞は細胞質分裂によって細胞質分裂され、その前駆体と遺伝的に同一の一対の細胞を形成します。

<ol>
	<li>Guertin, David A., Susanne Trautmann, and Dannel McCollum. "Cytokinesis in Eukaryotes." Microbiol. Mol. Biol. Rev. 66, no. 2 (2002年6月1日): 155–78.</li>
</ol>

有糸分裂と細胞質分裂

Mitosis And Cytokinesis

真核生物では、細胞分裂周期は、細胞増殖、DNA複製/染色体複製、娘細胞への染色体分配、そして最後に細胞分裂を含む、個別の調整された細胞プロセスに分割されます。 細胞周期は、その調節システムと細胞増殖に影響を与える細胞外シグナルによって厳密に調節されています。

細胞周期のプロセスは、（典型的なヒト細胞の場合）約 24 時間かけて、2 つの主要な区別可能な段階で発生します。 最初の段階は、間期の S 期における DNA 複製です。 第 2 段階は有糸分裂 (M) 期で、複製された染色体の 2 つの新しい核への分離 (有糸分裂) と細胞質分裂 (細胞質分裂) が含まれます。 2 つの相は間隔 (G1 ギャップと G2 ギャップ) によって分離されており、その間に細胞は複製と分裂の準備をします。

有糸分裂のプロセス

有糸分裂は、前期、前中期、中期、後期、終期という 5 つの異なる段階に分けることができます。 細胞質分裂は、(細胞に応じて)後期または終期に始まり、M期の一部ですが、有糸分裂の一部ではありません。

前期

細胞が有糸分裂に入ると、複製された染色体が凝縮し始め、コンデンシンとして知られるタンパク質の助けを借りて糸状の構造として見えるようになります。 有糸分裂紡錘体装置は、S 期に複製された中心体間に形成され始め、細胞の反対極に移動します。 紡錘体は、チューブリンタンパク質モノマーから構成される微小管と呼ばれる糸状構造で構成されています。 紡錘体微小管は凝縮した染色体に向かって伸び始めます。 リボソームを生成する核の要素である核小体が消失し、核の破壊が差し迫っていることを示します。

前中期

前中期の間、紡錘体装置からの微小管フィラメントは成長を続け、染色体の凝縮が終了します。 核膜が完全に破壊され、染色体が放出されます。 微小管の一部は放出された染色体に付着し、姉妹染色分体の各対のセントロメア上に存在する動原体と呼ばれるタンパク質構造に結合します。 反対極からの紡錘体微小管が動原体に付着し、凝縮された姉妹染色分体ペアを捕捉します。 染色体に付着していない紡錘体微小管 (極性および星状微小管) は、紡錘体を押し広げ、紡錘体極を細胞膜に固定するのに役立ちます。

中期

紡錘体微小管は、完全に凝縮した姉妹染色分体の各対を細胞の赤道に沿って、つまり中期板で整列させます。 これで細胞は分裂する準備が整いました。

後期

動原体構造に結合している反対側の紡錘体極からの微小管は、セントロメアで姉妹染色分体を短くして分離します。 染色分体を結合している粘着タンパク質が分解されます。 動原体微小管の短縮により、ペアの各染色分体 (現在は染色体と呼ばれています) が反対極に移動します。

終期

染色体が細胞の反対極に到達すると、凝集が解除され、ほどけてクロマチンが形成されます。 紡錘体微小管フィラメントは解重合してチューブリンモノマーになり、その後娘細胞の細胞骨格要素として利用されます。 核膜は染色体の各セットの周りに再集合します。

細胞質分裂

動物細胞の細胞質分裂中、アクチンフィラメントは原形質膜に収縮環を形成して切断溝を形成し、最終的に細胞を 2 つに挟みます。 植物細胞では、グルコース、酵素、構造タンパク質を運ぶゴルジ装置からの小胞が結合して、以前の中期板の位置に新しい細胞板を形成します。 成長する細胞板は両側の原形質膜と融合し、最終的には細胞を 2 つに分ける新しい細胞壁を形成します。

有糸分裂は完了し、親細胞と同一の 2 つの娘細胞が生成されます。 ほとんどのヒト細胞では、有糸分裂は約 24 時間の細胞周期のうち約 1 時間を占めます。

真核生物では、細胞分裂サイクルは、細胞増殖、DNA複製/染色体など、明確で調整された細胞プロセスに分割されます...

Education

JoVE Core

Anatomy and Physiology

解剖生理学

Unit 1

ユニット1

Essential Cellular Processes

細胞の基本的プロセス

KEY TERMS AND CONCEPTS

主要用語と概念

cell division: mitosis and cytokinesis

Cell division depends on mitosis and cytokinesis. Mitosis is the stage when the cell’s nucleus divides and the copied chromosomes are separated into two sets. Cytokinesis is the step that follows and splits the cell into two daughter cells.

These two processes work together to make sure each new cell receives genetic material and its own cytoplasm. Mitosis keeps the chromosome sets organized, while cytokinesis finishes the division of the whole cell. Together, they create two separate cells from one starting cell.

Cell Division: Mitosis and Cytokinesis

the central dogma

Central Dogma: DNA to Protein

The central dogma explains how genetic information flows in cells from DNA to RNA to protein. It is a core idea in molecular biology and helps show how genes influence cell function. DNA stores the instructions. During transcription, a cell copies a gene into RNA, which is a related nucleic acid. That RNA message can then be used in translation to build a protein. Proteins carry out many jobs in cells and help determine traits. The central dogma links the genetic code in DNA to the molecules...

replication in eukaryotes

Eukaryotic DNA Copying at the Replication Fork

Eukaryotic DNA copying happens at replication forks, where the two DNA strands separate and new strands are built. This process lets a cell make an exact copy of its genetic material before it divides. The transcript explains that eukaryotic replication follows the same basic steps seen in other DNA replication systems, but it takes place in cells with a nucleus. The replication machinery works on each separated strand as a template, so the new DNA matches the original sequence. This topic is...

types of rna

RNA Types in Gene Expression

RNA types play different roles in gene expression. RNA, or ribonucleic acid, helps carry and use genetic information in cells. The main types discussed here are messenger RNA, ribosomal RNA, and transfer RNA. Messenger RNA, or mRNA, carries the genetic code from DNA to the ribosome. The ribosome is the site where proteins are made. Ribosomal RNA, or rRNA, is a key part of the ribosome itself. Transfer RNA, or tRNA, brings the correct amino acids to the ribosome during protein building. These...

transcription

Transcription and RNA Synthesis

Transcription is the process of making RNA from a DNA template. It is a key step in gene expression, because cells use the DNA sequence to build an RNA copy that can carry the message forward. During transcription, RNA polymerase binds to DNA and reads one strand as the template. The enzyme links RNA nucleotides together in the correct order to form a growing RNA molecule. This copying step does not make DNA; it produces RNA. The transcript focuses on the central idea of transcription as DNA...

translation

Translation: mRNA to Protein

Translation is the step in gene expression where ribosomes use messenger RNA, or mRNA, to build a protein. The mRNA sequence carries the instructions copied from DNA. During translation, those instructions are read in order so the cell can make a specific chain of amino acids. This process depends on the ribosome and transfer RNA, or tRNA. The ribosome reads the mRNA, and tRNA brings the matching amino acids. As the chain grows, the amino acids are linked together to form a polypeptide, which...

regulation of expression at multiple steps

regulation-of-expression-at-multiple-steps

How Cells Control Gene Expression

Cells control gene expression at several stages, from making RNA to building protein. These checkpoints include transcription, RNA processing, RNA localization, and translation. Together, they help decide when a gene is used and whether a protein is made. Transcription is controlled by regulatory proteins. Transcription factors, activators, and repressors can start or slow the transcription of genes. After transcription, the cell makes a precursor RNA, also called pre-mRNA. Pre-mRNA must be...

what is the cell cycle?

Cell Cycle Stages in Cell Growth

The cell cycle is the process that controls cell growth and division. It explains how one cell makes two new cells. This process helps cells grow and reproduce.

interphase

Interphase and Cell Growth

Interphase is the part of the cell cycle when a cell grows and prepares to divide. It is a major stage of the cell cycle, and it comes before cell division begins. During interphase, the cell carries out its normal functions. It also copies its DNA so each new cell can receive a full set of genetic material. The cell may also build up the materials it needs for division. Interphase is not a single step. It includes phases such as G1, S, and G2, which help the cell grow, copy DNA, and get...

mitosis and cytokinesis

Cell division depends on mitosis and cytokinesis. Mitosis is the stage when the cell’s nucleus divides and the copied chromosomes are separated into two sets. Cytokinesis is the step that follows and splits the cell into two daughter cells. These two processes work together to make sure each new cell receives genetic material and its own cytoplasm. Mitosis keeps the chromosome sets organized, while cytokinesis finishes the division of the whole cell. Together, they create two separate cells...

the cell cycle control system

Cell Cycle Checkpoints and Cyclin Control

The cell cycle is controlled by checkpoints that help a cell move from one phase to the next and begin mitosis. This control system uses internal regulatory molecules and outside signals to send stop or advance instructions. It makes sure each step is finished before the cell moves forward. Cyclins and cyclin-dependent kinases, or Cdks, are the main regulators of the cell cycle. They act during the G1, G2, and M phases. These regulators work at specific checkpoints to keep cell division...

molecular factors affecting cell division

molecular-factors-affecting-cell-division

Cell Cycle Regulators That Control Division

Cell division is controlled by outside signals and by internal cell cycle regulators. Nearby cell death can encourage division, and human growth hormone (hGH) can also promote it. In contrast, too little hGH or crowded cells can slow or stop division. Inside the cell, regulator molecules help each stage finish correctly before the next stage begins. Some regulators act directly on the cycle, while others affect the activity or production of other regulatory proteins. These molecules can either...

what is meiosis?

Meiosis and the Formation of Gametes

Meiosis is the cell division process that forms gametes, or sex cells. It reduces the chromosome number so offspring can inherit the correct amount of genetic material. This process includes two successive divisions. First, one cell divides, and then the resulting cells divide again. These steps separate the genetic material in a controlled way. Meiosis helps explain how sexual reproduction passes traits from one generation to the next. It is a key topic in high school biology because it...

overview of cell signaling

Cell Signaling Pathways and Responses

Cell signaling pathways and responses help cells communicate and react to changes. Cells send signals to one another, and those signals can trigger a specific response in the target cell. A signal usually begins when a signaling molecule reaches a cell with the right receptor, which is a protein that receives the message. The receptor helps the cell recognize the signal and start the communication process. Inside the cell, the message can move through a signaling pathway. This pathway passes...

types of signaling molecules

Chemical Messengers in Cell Signaling

Chemical messengers help cells communicate during signaling. These signaling molecules carry information from one cell to another and guide how cells respond. Some signaling molecules are gases, while others are proteins or peptides. Small lipids can also act as signals. In addition, cells may use steroids, amino acids, and even ions as signaling molecules. Each type of signaling molecule has different properties and works in a different way. Together, these molecules let cells send specific...

g protein-coupled receptors

G Protein-coupled Receptor Signaling

G protein-coupled receptors are a major class of cell-surface receptors. They help cells detect signals outside the cell and pass that information inward. These receptors are important in many kinds of cell communication. When a signal binds to a G protein-coupled receptor, the receptor changes shape. That change activates a G protein inside the cell. The activated G protein can then start a signaling pathway. This signaling system includes the receptor, the G protein, and the downstream...

cellular differentiation

From Stem Cell to Specialized Cells

Cellular differentiation turns unspecialized cells into specialized cells with specific jobs. This process helps a complex organism, such as a human, develop from a single fertilized egg into a body with many cell types. Nerve cells, muscle cells, and epithelial cells are examples of the final cell types that appear during development. A zygote is the first cell after fertilization. It is a totipotent stem cell, which means it has very high differentiation potential and can form all cell types...

key terms and concepts

Learn how mitosis separates copied chromosomes and how cytokinesis divides the cell into two daughter cells in this high school biology page.

Cell Division: Mitosis and Cytokinesis | JoVE K12

anatomy and physiology

JoVE Core 解剖学と生理学では、人体の解剖学的および生理学的な詳細を、包括的で明確で魅力的なビデオ アニメーションで紹介します。このレッスン集は、人体の構造、コンポーネント、機能、要件に焦点を当てています。この知識を実際の医療および研究現場で応用することを実証する科学者による実際のビデオによって補完されています。

Cell Division: Mitosis and Cytokinesis

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