lab1 mitosis.ppt

8/11/2019 lab1 mitosis.ppt

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Dividing cells pass through a regular

sequence of cell growth and

division,known as

cell cycle.


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cell division: the process by which a celldivides into two daughter cells, each of

which has the same number of

chromosomes as the original.


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The cell cycle consists of five major phases

G1,S,G2,Mitosis,and cytokinesis.

Before a cell can begin mitosis and actuallydivide, it must replicate its chromosomes, and

synthesize the structures needed to carry out

mitosis and cytokinesis.These preparatory

processes occur during the G1,S,and G2

phases of the cell cycle, which are known

collectively as interphase.


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Types of divisions

Three types of cell division occur:

1. Binary fission,

2. Mitosis, and

3. Meiosis.

Binary fission, the method used by prokaryotes,produces two identical cells from one cell. The morecomplex process of mitosis, which also produces twogenetically identical cells from a single cell, is used bymany unicellular eukaryotic organisms for

reproduction. Multicellular organisms use mitosis for

1- Growth, 2- Cell repair, and 3-Cell replacement.


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Cell Cycle


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What is mitosis?

Mitosis is nuclear division plus cytokinesis andproduce two identical daughter cells byreplicating and dividing the original

chromosomes. Mitosis deals only with the segregation of the

chromosomes and organelles into daughtercells.

Replicated chromosomes consist of twomolecules of DNA known as chromatids. Thearea where both chromatids are in contact with

each other is known as the centromere.
http://www.emc.maricopa.edu/faculty/farabee/biobk/BioBookglossC.htmlhttp://www.emc.maricopa.edu/faculty/farabee/biobk/BioBookglossC.htmlhttp://www.emc.maricopa.edu/faculty/farabee/biobk/BioBookglossC.htmlhttp://www.emc.maricopa.edu/faculty/farabee/biobk/BioBookglossC.html


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Steps Of Mitosis

1- prophase,2- prometaphase, 3-

metaphase, 4- anaphase, and 5-

telophase.

Interphase is often included in

discussions of mitosis, but interphase is

technically not part of mitosis, but rather

encompasses stages G1, S, and G2 of thecell cycle.


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Interphase


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The kinetochoreis the point where microtubulesof the spindle apparatus attach.

The kinetochores are on the outer sides of the centromere.
http://www.emc.maricopa.edu/faculty/farabee/biobk/BioBookglossJK.htmlhttp://www.emc.maricopa.edu/faculty/farabee/biobk/BioBookglossJK.html


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Prophase

Prophaseis the first stage of mitosis proper. Chromatincondenses (remember that chromatin/DNA replicateduring Interphase), the nuclear envelope dissolves,

centrioles (if present) divide and migrate, kinetochoresand kinetochore fibers form, and the spindle forms. Thechromatin, diffuse in interphase, condenses intochromosomes. Each chromosomehas duplicated andnow consists of two sister chromatids. At the end ofprophase, the nuclear envelope breaks down intovesicles.
http://www.emc.maricopa.edu/faculty/farabee/biobk/BioBookglossPQ.htmlhttp://www.accessexcellence.org/RC/VL/GG/human.htmlhttp://www.accessexcellence.org/RC/VL/GG/human.htmlhttp://www.emc.maricopa.edu/faculty/farabee/biobk/BioBookglossPQ.html


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Prophase


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Metaphase

Metaphasefollows Prophase. The

chromosomes (which at this point consist of

chromatids held together by a centromere)

migrate to the equator of the spindle, where thespindles attach to the kinetochore fibers

The chromosomes align at the equitorial plate and

are held in place by microtubules attached to the

mitotic spindle and to part of the centromere.
http://www.emc.maricopa.edu/faculty/farabee/biobk/BioBookglossM.htmlhttp://www.emc.maricopa.edu/faculty/farabee/biobk/BioBookglossM.html


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Prometaphase


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Metaphase


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Anaphase

Anaphasebegins with the separation of thecentromeres, and the pulling of chromosomes

(we call them chromosomes after thecentromeres are separated) to opposite poles ofthe spindle.

The centromeres divide. Sister chromatids

separate and move toward the correspondingpoles.
http://www.emc.maricopa.edu/faculty/farabee/biobk/BioBookglossA.htmlhttp://www.emc.maricopa.edu/faculty/farabee/biobk/BioBookglossA.html


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Anaphase


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Telophase

Telophaseis when the chromosomes reach the poles oftheir respective spindles, the nuclear envelope reforms,chromosomes uncoil into chromatin form, and thenucleolus (which had disappeared during Prophase)

reform. Where there was one cell there are now twosmaller cells each with exactly the same geneticinformation. These cells may then develop into differentadult forms via the processes of development. Daughterchromosomes arrive at the poles and the microtubulesdisappear. The condensed chromatin expands and thenuclear envelope reappears. The cytoplasm divides,(phase: Cytokinesis).
http://www.emc.maricopa.edu/faculty/farabee/biobk/BioBookglossT.htmlhttp://www.emc.maricopa.edu/faculty/farabee/biobk/BioBookglossT.html


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Telophase


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Telophase 2


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lab1 mitosis.ppt

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