Cell Reproduction--Mitosis Section 8.2
Why do cells reproduce at all? Couldn’t they grow really, really big? Cells are limited to small sizes, therefore they must reproduce to make many cells instead of one big cell.
Diffusion would be too slow. Too many proteins would be needed. 1. Reasons why big cells are bad include: Diffusion would be too slow. Too many proteins would be needed. Cell membrane would not work properly. (surface area of cell) would not be able to increase as fast as the cell volume) (volume = l x w x h; surface area = l x w x 6)
Review: (2) all cells come from pre-existing cells This means that when a cell reproduces or divides, it creates two cells that are identical to the original.
3. This occurs not only because it is better to have many small cells, but also because an organism needs to grow or replace dead tissue. (growth and to replace dead tissue Results in population growth in unicellular (one-celled)organisms.
4. Chromosomes are structures that carry the coiled DNA. 5
5. Chromosome Centromere—hold together the halves Sister chromatid (the two halves of a replicated chromosome)
The Cell Cycle 6. The cell cycle is the steps a cell goes through during its life. .
A. interphase--a period of growth and DNA replication. Most of a cell’s life is spent in this stage
This is also where your DNA replicates Interphase The stage where the cell grows and does normal stuff This is also where your DNA replicates
Interphase Plant Cell Animal Cell Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
7.b. Mitosis B. Mitosis-- cell division resulting in 2 identical cells There are a series of steps after which 2 identical cells are formed, each with complete set of chromosomes.
8. Steps of Mitosis (PMAT) Prophase--prepares Metaphase--middle Anaphase--apart Telophase--two **use the terms to provide clues for what happens in each step**
Directions for diagrams: You will cut out descriptions for what occurs during the 4 steps of mitosis. As you read through the next slides, you will match the description with the diagram on your paper and glue or tape it down in the box provided.
Prophase First and longest step. Chromatin (DNA) coils into chromosomes. . nuclear membrane disappears. In animal cells, centrioles and spindle fiber have formed Prophase
Centrioles move to poles of cell and make spindle fibers The 1st step of Mitosis,,,,,,Prophase DNA thickens into chromosomes Nuclear membrane disappears Centrioles move to poles of cell and make spindle fibers
Prophase Plant Cell Animal Cell Spindle fibers Centrioles Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
Metaphase Chromosomes attach to the spindle fibers at the centromere. chromosomes line up in the middle of the cell, so each sister chromatid is facing a pole.
Metaphase Plant Cell Animal Cell Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
Anaphase Sister chromatids are pulled apart towards opposite poles.
Anaphase Plant Cell Animal Cell Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
Telophase Chromatids reach opposite poles and begin to uncoil. Two new nuclei are formed. new cell membrane begins to form
Telophase Plant Cell Animal Cell Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
In animal cells it pinches in two this is called a Cleavage Furrow 10. Cytokinesis….this is when the cell actually splits in two and divides the cytoplasm in half In animal cells it pinches in two this is called a Cleavage Furrow
Cytokinesis occurs after mitosis Cell membrane moves inward to create two daughter cells – each with its own nucleus with identical chromosomes.
Cytokinesis In plants the cell just builds a new cell wall straight down the middle
Animal Mitosis -- Review Interphase Prophase Metaphase Anaphase Telophase
Plant Mitosis -- Review Interphase Prophase Metaphase Anaphase Telophase
Cell Cycle 30
2 2 2 4
http://207.207.4.198/pub/flash/8/8.html
Mitosis Animation http://www.cellsalive.com/mitosis.htm