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.

• 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.

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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.

• .

7. a. interphase

• A. interphase--a period of growth and DNA replication.

• Most of a cell’s life is spent in this stage

The stage where the cell grows and does normal stuff

This is also where your DNA replicates

Interphase

Animal Cell Plant 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

The 1st step of Mitosis,,,,,,Prophase

DNA thickens into chromosomes

Centrioles move to poles of cell and make spindle fibers

Nuclear membrane disappears

Animal Cell Plant Cell

Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm

Spindle fibers

Centrioles

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.

Animal Cell Plant Cell

Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm

Anaphase

• Sister chromatids are pulled apart towards opposite poles.

Animal Cell Plant 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

Animal Cell Plant Cell

Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm

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

• 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

                                              

              

Interphase

                                             

               

Plant Mitosis -- ReviewInterphase

                                                        

    

Prophase

                                                       

     

Metaphase

                                                        

    

Anaphase

                                                       

     

Telophase

                                                        

    

Interphase

                                                       

     

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• http://207.207.4.198/pub/flash/8/8.html

http://www.cellsalive.com/mitosis.htm