Cell Division - MitosisCell Division - Mitosis

So WHY do cells divide?So WHY do cells divide?

Smaller cells have a larger surface area (cell membrane) to volume (cytoplasm/organelles) ratio and therefore are more efficient in getting things in (nutrients) and out (wastes) of cells.

Smaller cells have a larger surface area (cell membrane) to volume (cytoplasm/organelles) ratio and therefore are more efficient in getting things in (nutrients) and out (wastes) of cells.

When do cells divide by mitosis?

a) during growth

b) for repair (regeneration)

c) reproduction in single cell organisms

During Growth

For Repair (Regeneration)

Reproduction- for single celled organisms

MITOSISMITOSIS

Cell division in body/somatic cells

Cell division in body/somatic cells

One chromosome after duplication/replication has

2 chromatids!

One chromosome after duplication/replication has

2 chromatids!

Sister chromatids made during S phase of Interphase

It goes from B to C during Anaphase

Some vocabSome vocab

Chromosomes- long thread of DNA in nucleus - there are 46 chromosomes in each cell

Genes - small section of chromosome/DNA Chromatids- each duplicated strand of

chromosome. Centromere- structure that holds the

identical pairs of chromosomes (chromatids) together.

Chromosomes- long thread of DNA in nucleus - there are 46 chromosomes in each cell

Genes - small section of chromosome/DNA Chromatids- each duplicated strand of

chromosome. Centromere- structure that holds the

identical pairs of chromosomes (chromatids) together.

Cell Cycle Cell Cycle

Interphase G1 = first growth

phase ~ 9 hrs S = Synthesis phase

~ 10 hrs G2 = second growth

phase ~ 2 hrs

Interphase G1 = first growth

phase ~ 9 hrs S = Synthesis phase

~ 10 hrs G2 = second growth

phase ~ 2 hrs

•Cell cycle includes interphase & mitosis

•Interphase is the longest part of the cell cycle.

Cell cycle memory aidCell cycle memory aid Interphase, Prophase, Metaphase, Anaphase,

Telophase, Cytokinesis Interphase, Prophase, Metaphase, Anaphase,

Telophase, Cytokinesis

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InterphaseInterphase

• Parent Cell – “Resting Phase”• Cell is undergoing normal cell activities (Protein Synthesis,

etc..)• Not really ‘at rest’, but not actively dividing!

• The Chromosomes are in an extended form and seen as chromatin (DNA+protein) - dense mass.

• The nucleus is visible.• Cell size increases• DNA of the chromosome is replicated.

ProphaseProphase

• Chromatin condense so that they are seen to consist of 2 chromatids joined by a centromere.

• The centrioles move toward opposite poles of the cell.• Spindle fibers are produced & extend from each

centrosomes.• Nuclear membrane starts to disappear• Nucleolus is no longer visible

MetaphaseMetaphase

• The chromosomes line up at the equatorial plate.• The spindle fibers from each centrioles are attached

to the centromeres of the chromosomes.• The nuclear membrane has completely

disappeared.

AnaphaseAnaphase

• The centromeres splits & the sister chromatids separate as each is pulled to an opposite pole.

• Single strand chromatid are now called chromosomes

TelophaseTelophase

• The chromosomes become longer, thinner, & less distinct• New nuclear membrane forms• The nucleolus reappears• Cytokinesis begins

CytokinesisCytokinesis

Cytoplasm divides Cleavage furrow- cytokinesis in animal cells Cell plate forms- cytokinesis in plant cells

Two daughter cells are formed with their own nucleus

Cytoplasm divides Cleavage furrow- cytokinesis in animal cells Cell plate forms- cytokinesis in plant cells

Two daughter cells are formed with their own nucleus

CELL IN INTERPHASE….

Daughter Cells – “Resting Phase”See the chromatin

IN SUMMARY-Mitosis is:NuclearDuplication

-CytokinesisIs Cytoplasmic

division

Mitosis & Chromosome Terms (ploidy = number)Mitosis & Chromosome

Terms (ploidy = number)

Monoploid or haploid(n)- half the normal condition in animals (ie. Sex cells)

Diploid(2n)- normal chromosome condition Tetraploid(4n)- 2times normal condition

Humans: n=23 chromosometherefore…

46 chromosome in our body cells &23 chromosomes in our sex cells

If 23 = n; then 46 = 2n; and 92 = 4n

Monoploid or haploid(n)- half the normal condition in animals (ie. Sex cells)

Diploid(2n)- normal chromosome condition Tetraploid(4n)- 2times normal condition

Humans: n=23 chromosometherefore…

46 chromosome in our body cells &23 chromosomes in our sex cells

If 23 = n; then 46 = 2n; and 92 = 4n

Chromatid

ChromosomeChromosome

Interphase: The DNA Replicates & chromosomes are doubled

Chromosome

Anaphase: the centromere splits and the 2 chromatids are now 2 chromosomes

Interphase: 2n Chromosome Condition:

Prophase: 2n

Metaphase: 2n

Telophase: 4n

Anaphase: 4n

INTERPHASE

METAPHASE

TELOPHASE

PROPHASE

ANAPHASE

DAUGHTER CELLS

METAPHASE

ANAPHASE

TELOPHASE

LAB B-1-3 Drawings:Whitefish Blastula

http://www.iknow.net/CDROMs/cell_cdrom/cellmovies.shtml

http://www.sci.sdsu.edu/multimedia/mitosis/mitosis_control.html

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

Mitosis Tutorial for Studentshttp://www.biology.arizona.edu/Cell_bio/tutorials/cell_cycle/cells3.html

http://hrsbstaff.ednet.ns.ca/bfougere/science9assist.htm