1.6 Zellteilung

Der Zellzyklus Zykline regulieren den Zellzyklus G1: Zellwachstum Zytokinese Telophase und Anaphase Metaphase G1: Zellwachstum und Differenzierung Prophase Mitose G2: Zellwachstum Figure: 11-3 Title: The eukaryotic cell cycle Caption: The eukaryotic cell cycle consists of interphase and mitotic cell division. Some cells enter the G0 phase and may not divide again. Exercise Give an example of an adult animal body tissue in which many cells are likely to be in the cell division phase of the cell cycle, and an example in which few dividing cells would be found. Interphase S: Replikation der DNA Zykline regulieren den Zellzyklus

Mitose Die Teilung des Nukleus in zwei genetisch identische Tochternuklei

Chromosomen

Chromosomen werden bei der Mitose durch Supercoiling kondensiert. DNA Histon Proteine Figure: 11-5 Title: Chromosome structure Caption: A eukaryotic chromosome contains a single, linear DNA double helix (top), which, in humans, is about 14 to 73 millimeters (mm) long and 2 nanometers (nm) in diameter. The DNA is wound around proteins called histones, forming nucleosomes (middle); this reduces the length by about a factor of 6. Other proteins coil up adjacent nucleosomes, much like a Slinky toy, reducing the length by another factor of 6 or 7. The coils of DNA and their associated proteins are attached in loops to still larger coils of protein "scaffolding" to complete the chromosome (bottom). All of this wrapping, coiling, and looping makes the extended interphase chromosome roughly 1000 times shorter than the DNA molecule it contains. Still other proteins produce about another 10-fold condensation during cell division (see Fig. 11-6).

Chromosomen werden bei der Mitose durch Supercoiling kondensiert. Figure: 11-5 top Title: Chromosome structure top Caption: A eukaryotic chromosome contains a single, linear DNA double helix (top), which, in humans, is about 14 to 73 millimeters (mm) long and 2 nanometers (nm) in diameter. The DNA is wound around proteins called histones, forming nucleosomes (middle); this reduces the length by about a factor of 6. Other proteins coil up adjacent nucleosomes, much like a Slinky toy, reducing the length by another factor of 6 or 7. The coils of DNA and their associated proteins are attached in loops to still larger coils of protein "scaffolding" to complete the chromosome (bottom). All of this wrapping, coiling, and looping makes the extended interphase chromosome roughly 1000 times shorter than the DNA molecule it contains. Still other proteins produce about another 10-fold condensation during cell division (see Fig. 11-6).

Chromosomen werden bei der Mitose durch Supercoiling kondensiert. Figure: 11-5 bottom Title: Chromosome structure bottom Caption: A eukaryotic chromosome contains a single, linear DNA double helix (top), which, in humans, is about 14 to 73 millimeters (mm) long and 2 nanometers (nm) in diameter. The DNA is wound around proteins called histones, forming nucleosomes (middle); this reduces the length by about a factor of 6. Other proteins coil up adjacent nucleosomes, much like a Slinky toy, reducing the length by another factor of 6 or 7. The coils of DNA and their associated proteins are attached in loops to still larger coils of protein "scaffolding" to complete the chromosome (bottom). All of this wrapping, coiling, and looping makes the extended interphase chromosome roughly 1000 times shorter than the DNA molecule it contains. Still other proteins produce about another 10-fold condensation during cell division (see Fig. 11-6).

Verdoppeltes Schwester Chromosom Chroma- (2 DNA Doppel helices) tiden Figure: 11-UN2 Title: Duplicated chromosome

Zwei getrennte Chromosomen Figure: 11-UN3 Title: Daughter chromosomes

Die Phasen der Mitose

Chromatin Chromosomen Zellpol kondensieren Zentriolen Spindelfasern INTERPHASE MITOSE Chromatin Chromosomen kondensieren Zellpol Figure: 11-8 left Title: Mitotic cell division in an animal cell left Caption: Question What would the consequences be if one set of sister chromatids failed to separate at anaphase? Zentriolen Spindelfasern SPÄTE INTERPHASE FRÜHE PROPHASE SPÄTE PROPHASE METAPHASE Die verdoppelten Chromosomen sind lang und noch nicht kondensiert. Sie heißen Chromatin. Chromosomen beginnen sich zu kondensieren. Kernmembran löst sich auf. Spindelfasern verbinden sich mit dem Zentromer eines jeden Chromosomens. Die Chromosomen ordnden sich in der Äquatorialebene an.

INTERPHASE Figure: 11-8 right Title: Mitotic cell division in an animal cell right Caption: Question What would the consequences be if one set of sister chromatids failed to separate at anaphase? ANAPHASE TELOPHASE ZYTOKINESE INTERPHASE DER TOCHTERZELLEN Die Schwesterchromatiden werden zu den Zellpolen Gezogen. Die Chromosomen dekondensieren. Es bildet sich eine neue Kernmembren. Die Zellen trennen sich. Bei Pflanzenzellen bildet sich eine Zellwand. Jede Tochterzelle ist genetisch identisch..

späte Prophase Zytokinese Interphase Telophase Interphase Prophase 1 5 Interphase Telophase 2 6 Interphase Prophase 3 7 Anaphase Metaphase 4 8

Zytokinese bei Tier- und Pflanzenzellen Figure: 11-9 part a Title: Cytokinesis in an animal cell part a Caption: (a) A ring of microfilaments just beneath the plasma membrane contracts around the equator of the cell, pinching it in two.

Unkontrollierte Mitosen Krebs Mutagene Onkogene Unkontrollierte Mitosen Metastasen Tumor

Mitotischer Index Zahl der Zellen einer Zellgruppe, die sich zu einem bestimmten Zeitpunkt teilen. Der normale Index der meisten Körpergewebe ist heute bekannt; weicht ein Gewebe stark davon ab, kann das ein Hinweis auf Krebs sein.