Recap on Cell Size cells are limited in their size because of 3 things: –1. Diffusion –2. DNA...
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Transcript of Recap on Cell Size cells are limited in their size because of 3 things: –1. Diffusion –2. DNA...
![Page 1: Recap on Cell Size cells are limited in their size because of 3 things: –1. Diffusion –2. DNA –3. Food Requirements Therefore, Cells have 2 methods of.](https://reader035.fdocuments.net/reader035/viewer/2022070407/56649e355503460f94b23962/html5/thumbnails/1.jpg)
Recap on Cell Size
• cells are limited in their size because of 3 things:– 1. Diffusion– 2. DNA– 3. Food Requirements
• Therefore, Cells have 2 methods of dealing with cell size:– Altered Shape– Cell Division
• We are going to learn how cells Divide!
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Cell Theory & Chromosomes
• Recall that Cell theory states “all cells come from preexisting cells.”
• Cell Division results in two cells that are identical to the original, parent cell
• Chromosomes – “colored bodies” that contain genetic material.
• It is the identity of the cell• Accurate transmission of
chromosomes during cell division is critical.
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The Cell Cycle • Cell Cycle – sequence of
growth and division of a cell• Broken into 2 Parts:
– Interphase : Growth– Mitosis : Division
• A cell spends most of its life in INTERPHASE
• Cell division is during mitosis• One final process, division of the
cytoplasm, cytokinesis, takes place after mitosis.
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Cell Cycle - Interphase• During Interphase…
– Cell grows in size– Carries on metabolism– Replicates chromosomes
• Composed of 3 Phases:– G1 : Chromosomes are not
yet visible, rapid protein synthesis due to growth
– S : Chromosomes are replicated in the nucleus (sister chromatids)
– G2 : Chromosomes shorten & coil, protein synthesis prepares for Mitosis, centrioles prepare to make the mitotic spindle, cell organelles are replicated
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Cell Cycle: Mitosis - Prophase
• There are 4 Stages of Mitosis• 1.) PROPHASE
– First and longest stage– Chromatin coils up into visible
chromosomes– Sister Chromatids are visible (2 exact
copies of DNA for the 2 new cells) from interphase
– Sister Chromatids are held together by a centromere
– Nucleus begins to disappear– Nucleolus disintegrates– Animal Cells – Centrioles Migrate to the
poles for chromatin separation– Spindle forms – for sister chromatid
separation. In Plant cells the spindle forms without centrioles.
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Chromatin – long strands of DNA wrapped around proteins, it only becomes chromosomes for replication and protein synthesis.Centromere – Structure that holds sister chromatids together. Plays a role in chromosome movement during mitosis. By their characteristic location, centromeres also help scientists identify and study chromosomes.
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Cell Cycle: Mitosis - Metaphase• During Metaphase…
– Short second phase– Doubled chromosomes become
attached to the spindle fibers by their centromeres
– Chromosomes are pulled by the spindle fibers
– Begin to line up on the midline or equator of the spindle
– Each sister chromatid is attached to its own spindle fiber
– One spindle fiber extends to one pole, the other to the opposite pole
– Ensures that each new cell receives an identical and complete set of chromosomes.
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Cell Cycle: Mitosis - Anaphase• During Anaphase…
– Third phase of mitosis– Separation of sister
chromatids at the beginning
– Centromeres split apart– Chromatid pairs from each
chromosomes separate from each other
– Chromatids are pulled apart by the shortening of the microtubles in the spindle fibers
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Cell Cycle: Mitosis - Telophase• In Telophase…
– The fourth and final stage– Begins as chromatids reach the
opposite poles of the cell– Many of the Mitotic changes that took
place are reversing for the two new cells
– Chromosomes unwind for protein synthesis
– Spindle breaks down– Nucleolus reappears– New nuclear envelope forms
around each set of chromosomes– A new double membrane begins to
form around the 2 new nuclei
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Mitosis - Cytokinesis• Following telophase, the
cell’s cytoplasm divides in a process called Cytokinesis
• In Animal Cells – plasma membrane pinches in along the equator
• In Plant Cells – a cell plate is laid down across the cell’s equator. A cell membrane forms around each cell, and new cell walls form on each side of the cell plate until separation is complete.
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Your Turn!Place the following images in order of Mitosis with numbers, and give the name of the cycle. Let interphase be step 5.
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How did you do?
2 - Metaphase4 - Telophase 1 - Prophase
5 - Interphase3 - Anaphase
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Results of Mitosis• Mitosis gives genetic
continuity• Daughter cells will carry out
the same process or job as the parent cell
• Results in groups of cells– Atoms form Molecules– Molecules form Cells– Cells form Tissues– Tissues form Organs– Organs form Organ systems– Organ Systems form an
Organism
• Remember! The Cell is STILL the most basic unit of organization.