negatively charged double stranded wraps around histones chromosome=chromatid + kinetochore 46...

Chromosomes and Cell Division

DNADNA Negatively charged

Double stranded

Wraps around histones

CHROMOSOME=chromatid + kinetochore

46 chromosomes in humans

DNA Limits Cell Size

Cell cannot survive unless there is enough DNA to support the protein needs of the cell

Some really large cells are multi-nucleated› More nuclei = › more DNA = › quick protein making

Cell Reproduction

Cell Division= making 2 daughter cells from one parent cell

AKA : Asexual Reproduction

Happens in all cells

New cells are genetically identical!

Prokaryote Cell Division

Bacteria Circular DNA Produce 2

daughter cells by BINARY FISSION

DNA copied Know steps!

How do little elephants grow up to be BIG elephants?

Only happens in eukaryotes.Only happens in somatic

cells.Cells reproduce constantly.

The process of mitosis begins after a sperm

fertilizes an egg.

Skin cancer - the abnormal growth of skin cells - most often develops on skin exposed to the sun.

Animated Mitosis Cyclehttp://www.cellsalive.com/mitosis.htm

• Interphase

• Prophase

• Metaphase

• Anaphase

• Telophase & Cytokinesis

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

• Chromosomes are copied (# doubles)• Chromosomes appear as threadlike coils

(chromatin) at the start, but each chromosome and its copy(sister chromosome) change to sister chromatids at end of this phase

CELL MEMBRANENucleus

Cytoplasm

Animal Cell Plant Cell

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

• Mitosis begins (cell begins to divide)• Centrioles appear and begin to move to

opposite end of the cell. • Spindle fibers form between the poles.• Nuclear membrane breaks down.

CentriolesSister chromatids

Spindle fibers



Spindle fibers

Centrioles

• Meta = Middle• Centromere/Kinetochore replicate• Sister Chromatids (or pairs of

chromosomes) attach to the spindle fibers.• Chromosomes line up along the equator

Centrioles

Spindle fibers

• Chromatids (or pairs of chromosomes) separate and are pulled to the poles

• Pulled by spindle fibers.

Centrioles

Spindle fibers

• Two new nuclei form.• Nuclear Membrane reforms• Spindle Fibers fall apart• Chromosomes uncoil into chromatin (thread)• Cleavage: membrane pinches to make 2 identical cells

(Cytokinesis)

NucleiNuclei

Chromatin

• Cell membrane moves inward to create two daughter cells – each with its own nucleus with identical chromosomes.

Plant Mitosis -- ReviewInterphase

Prophase

Metaphase

Anaphase

Telophase

Cytokinesis

Animal Mitosis -- Review

Interphase

Prophase

Metaphase

Anaphase

Telophase

Cytokinesis

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- Cell Division

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Why is mitosis important?

Growth and replacement of dead, lost, or damaged cells

Ensures each daughter cell gets a complete and exact copy of the genetic material from the parent cell in the quickest, most efficient way

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Means division of the Means division of the cytoplasmcytoplasm

Division of cell into two, Division of cell into two, identical halves called identical halves called daughter cellsdaughter cells

In plant cells, cell plate forms In plant cells, cell plate forms at the equator to divide cellat the equator to divide cell

In animal cells, cleavage In animal cells, cleavage furrow forms to split cellfurrow forms to split cell

copyright cmassengale

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Cleavage furrow Cleavage furrow in animal cellin animal cell

Cell plate in plant Cell plate in plant cellcell


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Parent CellParent Cell

Two Two identical identical daughter daughter cellscells


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If mitosis is not If mitosis is not controlled, controlled, unlimited cell unlimited cell division occurs division occurs causing cancerous causing cancerous tumorstumors

Oncogenes are Oncogenes are special proteins special proteins that increase the increase the chance that a chance that a normal cell normal cell develops into a develops into a tumor cell tumor cell Cancer cellsCancer cells


negatively charged double stranded wraps around histones chromosome=chromatid + kinetochore 46...

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