![]() In addition, chromosomal DNA is duplicated during a subportion of interphase known as the S, or synthesis, phase. For this reason, the enzyme complexes that copy DNA have the greatest access to chromosomal DNA during interphase, at which time the vast majority of gene transcription occurs. ![]() A precise estimate of the difference is not possible, but during interphase, chromatin may be hundreds or even thousands of times less condensed than it is during mitosis. The difference in DNA compaction between interphase and mitosis is dramatic. With very few exceptions, mitosis occupies a much smaller fraction of the cell cycle than interphase. Today, scientists know that Flemming had successfully distinguished chromosomes in the interphase portion of the cell cycle from chromosomes undergoing mitosis, or the portion of the cell cycle during which the nucleus divides (Figure 1). (We still use the word "chromatin" today, albeit in a more biochemical sense to refer to complexes of nuclear DNA and protein.) Specifically, in some cells, chromatin appeared as an amorphous network, although in other cells, it appeared as threadlike bodies that Flemming named "mitosen." Based on his observations, Flemming had the insight to propose that chromatin could undergo reversible transformations in cells. Remain alive and functioning without dividingģ.In his pioneering studies of mitosis, Flemming noted that the nuclear material, which he named " chromatin" for its ability to take up stains, did not have the same appearance in all cells. New nuclear envelope forms Telophase New nucleoli appears Telophase Mitotic spindle breaks up Telophase Division of parent cell's cytoplasm and organelles Cytokinesis When does cytokinesis begin? late anaphase or early telophase with the formation of cleavage furrow What happens when cytokinesis is complete? Interphase begins Results in haploid cells Meiosis What are the three destines of a cell 1. The microtubules disappear or change forms. Extend between the 2 centrosomes What is the spindle responsible for? Separation of chromatid to each new daughter cell Where centromeres line up at the exact center of the mitotic spindle Metaphase plate or Equatorial Plane Centrioles on opposite poles Metaphase Chromatids are formed from chromosomes which then allow separation to happen Metaphase Splitting and separation of centromeres and the movement of the two sister chromatids of each pair towards opposite poles of the cell Anaphase Sister chromatids move toward opposite poles of the cells Anaphase Sister chromatids are now called daughter chromosomes Anaphase The movement of the sister chromatids is caused by what? Shortening of microtubules/spindle Chromosomes appear V-shaped as they are dragged towards the poles of the cell Anaphase What are the V-shaped chromosomes? daughter chromatin being pulled to opposite poles closer to centrioles When does Telophase begin? When identical sets of chromosomes at the opposite poles of the cell uncoil and revert to their threadlike chromatin form. bind to kinetochore protein on centromereģ. ![]() ![]() ![]() Replication of chromosomes and DNA replicated Interphase: S Cytoplasmic growth and duplication of internal cell Interphase: G2 Cell never divides again (all cells go through this) Interphase: G0 Chromatin condenses and shortens into chromosomes Prophase Pair of identical chromatids held together by a centromere Chromosome Microtubules appear for further replication Prophase Nucleus and Nuclear envelope disappears Prophase Each centrosome moves to different ends Prophase What are the three types of microtubules 1. ![]()
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