Amy Brown Science Stuff Limits to Cell Growth Why do cells divide? Instead of dividing, why dont cells just grow larger There are two main reasons why cells divide rather than continuing to grow larger and larger: The larger a cell becomes, the . . more
demands the cell places on its DNA. If the cell grows too large, it will have trouble moving enough nutrients and wastes across the cell membrane. Cell Division Cell division is the process by which cellular material is divided between two new daughter cells.
1 Mother Cell 2 Daughter cells. The two daughter cells will be. identical to each other and to the mother cell. Each daughter is half the size of the parent cell, but immediately begins growing. A typical human cell has about 2 meters of DNA. Before the cell can divide, all of this DNA must be copied and then the two copies separated so that each daughter cell ends up
with a complete set of DNA. Each species has a characteristic number of chromosomes in each cell nucleus; humans have 23 Chromosomes During Eukaryotic Cellcell Division copy its chromosomes Each must first __________________ before cell division occurs. Each daughter cell gets a complete copy of that information.
Cell division occurs in two main stages: Mitosis The division of the nucleus Cytokinesis The division of the cytoplasm The Cell Cycle The cell cycle is: The series of events that cells go through as they grow and divide. The cell cycle is the life of the cell from the time it is first formed from a dividing parent cell until its own division into two cells. During the cell cycle: 1. A cell grows. 2. The cell prepares for division.
3. The cell divides to form two daughter cells. We are now going to break mitosis down into its individual stages and see what is going on in each stage. Interphas e centrioles nuclear
membrane nucleolus chromosome s Of the cell cycle, interphase accounts for 90% of the time. well defined and bounded by Nucleus is ___________ nuclear the membrane ________________. Outside of the nucleus are centrioles two ____________. Their function
is to: the microtubules into a spindle. organize They will begin to move apart as spindle microtubules grow Remember! Mitosis has 4 stages: 1. Prophase 2. Metaphase 3. Anaphase 4. Telophase Prophase Early prophase The chromosomes coil centrioles
and thicken and Spindle become distinct from made of one another. The microtubule s chromosomes are now Chromatids visible. disappears The nucleolus __________. connected by a The chromosomes centromere are doubled
. throughout their length. Each half of the double chromosome chromatid is a ____________. centromere The chromatids are connected by a ___________. The centrioles __________ separate and start moving to opposite ends ofspindle the cell. A ________ made of ____________ begins to form. microtubul Prophase The ___________________
nuclear membrane fragments and the microtubules invade the nuclear area. The spindle is completely formed. The spindle is a structure that will help separate the to chromosomes _______________________. chromatids During prophase the pairs of __________ become attached to the fibers of the
spindle. Late prophase centrioles Microtubule s form a complete chromatids spindle. centrioles The centrioles have moved to the opposite poles, forming the spindle
Metaphas The centrioles eare now at centrioles opposite sides of the cell. The spindle fibers will push and pull the chromosomes. The chromosomes chromatids centrio
les Spindle composed of microtubule s Each chromosome is connected to a spindle fiber at its centromere. Anaphas The e centromeres divide and the chromatids
The microtubules move toto shorten begin opposite and this sides pulls the ofchromatids the cell. apart to opposite sides of the cell. Chromatid s are being pulled to opposite sides of the cell.
Shortening of the microtubul es By the end of anaphase, the two ends of the cell have equivalent and complete sets of chromosomes. Telophase Nuclear membrane begins to form. Nuclear
membrane is returning. Nucleolus returns. The cell begins to pinch in. The end result is two cells that are exact copies of Can you name these phases? 23Metaphase Anaphase 5Telophase
Interphase 1Prophase 4 - Cytokinesis two___________ nuclei At the end of mitosis, have been formed. Each nucleus has an chromosome identical set of _________________. s Cytokinesis is: the division of the cytoplasm. Cytokinesis
usually occurs at the same time as telophase. Cytokinesis in Animal Cells Cytokinesis in Plant Cells M I T O S I S
Takes between 30 minutes and 2 hours. One Mother Cell = Two Daughter cells. The two daughter cells are identical to the mother Results of Mitosis Importan ce of Mitosis
In unicellular plants and animals, it results in new offspring by asexual reproduction. In multicellular organisms, it results in the growth and repair of the organism. The two new cells are exact duplicates. Insures that the new cells will be able to carry on the same functions as the mother cell.
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