Mitosis & Meiosis CHAPTER8. CHROMOSOMES Chromosome: DNA in a Eukaryotic cell that is tightly coiled and compacted in the cell nucleus Chromosome: DNA

Mitosis & MeiosisMitosis & MeiosisCHAPTER8CHAPTER8

CHROMOSOMESCHROMOSOMES Chromosome: DNA in a Eukaryotic cell that is Chromosome: DNA in a Eukaryotic cell that is

tightly coiled and compacted in the cell tightly coiled and compacted in the cell nucleusnucleus

Histones:Histones:Proteins inProteins in

Which DNA isWhich DNA is

Tightly wrappedTightly wrapped

Around thatAround that

Help maintainHelp maintain

The shape ofThe shape of

The chromosomes The chromosomes

Chromosome Structure: Chromosome Structure:

Chromosome Chromosome numbers:numbers:

Chromosomes are categorized as Chromosomes are categorized as either sex chromosomes or either sex chromosomes or autosomesautosomes

Sex chromosomes: chromosomes Sex chromosomes: chromosomes that determine the sex of an that determine the sex of an organismorganism

Autosomes: all other Autosomes: all other chromosomes in an organismchromosomes in an organism

Homologous chromosomes: one copy Homologous chromosomes: one copy of each autosome from each parent. of each autosome from each parent. The two copies of each autosome are The two copies of each autosome are called homologous chromosomescalled homologous chromosomes

Diploid: cells having 2 setsDiploid: cells having 2 sets

Of chromosomes Of chromosomes

Haploid: cells which contain Haploid: cells which contain

only one set of chromosomesonly one set of chromosomes

Karyotype: Karyotype: photomicrograph of the photomicrograph of the chromosomes in a cellchromosomes in a cell

Cell division in prokaryotes: Cell division in prokaryotes: Binary fissionBinary fission

Mitosis:Mitosis: If a cell wants to make a duplicate of itself, it If a cell wants to make a duplicate of itself, it

first must copy its DNA (part of a first must copy its DNA (part of a chromosome).chromosome).

The copies then must be separated & sorted The copies then must be separated & sorted into two sides of the cell.into two sides of the cell.

The cell then splits in two. Part of each parent The cell then splits in two. Part of each parent is carried to the two new cells. is carried to the two new cells.

Results in cells such as internal organs, skin, Results in cells such as internal organs, skin, bones, blood, etc. bones, blood, etc.

MitosisMitosis

Mitosis animations:Mitosis animations: http://www.youtube.com/watch?v=VlN7K1-9QB0

http://www.youtube.com/watch?v=VlN7K1-9QB0

Interphase Interphase occurs just before occurs just before Mitosis begins:Mitosis begins:

Cells spend most of the cell cycle in interphase

During g1 – offspring cells grow to mature size

During S phase- cells DNA is copied

During g2 phase- cell prepares for cell division (mitosis) http://www.bioweb.uncc.edu/1110Lab/notes/notes1/lab6.htm

G0 phaseG0 phase

Cells can sometimes exit the cell Cells can sometimes exit the cell cycle usually from the g1 phase and cycle usually from the g1 phase and enter s state called g0enter s state called g0

During g0, cells do not copy their During g0, cells do not copy their DNA and do not prepare for cell DNA and do not prepare for cell division. division.

Many cells in the human body are in Many cells in the human body are in the g0 phasethe g0 phase

InterphaseInterphase

Animal cellAnimal cell Plant cellPlant cell

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

11stst step in Mitosis: step in Mitosis: Prophase (preparation phase)Prophase (preparation phase)

http://www.bioweb.uncc.edu/1110Lab/notes/notes1/lab6.htm

The DNA recoils, and the chromosomes condense; the nuclear membrane disappears, and the mitotic spindles begin to form.

MitosisMitosis Prophase Prophase



22ndnd step in Mitosis: step in Mitosis:metaphase metaphase

The The chromosomes chromosomes line up the line up the middle of the cell middle of the cell with the help of with the help of spindle fibers spindle fibers attached to the attached to the centromere of centromere of each replicated each replicated chromosome. chromosome.


MitosisMitosis Metaphase Metaphase



33rdrd step in Mitosis: step in Mitosis: Anaphase (separation phase)Anaphase (separation phase)

The The chromosomes chromosomes split in the split in the middle and the middle and the sister chromatids sister chromatids are pulled by the are pulled by the spindle fibers to spindle fibers to opposite poles of opposite poles of the cell. the cell.


MitosisMitosis Anaphase Anaphase



44thth step in Mitosis: step in Mitosis: TelophaseTelophase

spindle fibers spindle fibers dissasemble,dissasemble, and the and the chromosomes return to chromosomes return to a less condensed a less condensed chromatin state.chromatin state.

A nuclear envelope forms A nuclear envelope forms around each set of around each set of chromosomes and a chromosomes and a nucleolus forms in each nucleolus forms in each of the newly formed of the newly formed cells. cells.


MitosisMitosis Telophase Telophase



After Mitosis:After Mitosis: CytokinesisCytokinesis

The actual splitting ofThe actual splitting of

the daughter cells into the daughter cells into

two separate cells is two separate cells is

called cytokinesis andcalled cytokinesis and

occurs differently in occurs differently in

both plant and animalboth plant and animal

Cells.Cells.

Beginning of cytokinesis in a plant: a plate forms along the

midline of the dividing cell

Beginning of cytokinesis in an animal: cell membrane pinches in at the middle

of the dividing cell(this is called a cleavage furrow)

IInterphasenterphasePProphaserophaseMMetaphaseetaphaseAAnaphasenaphaseTTelophaseelophaseCCytokinesisytokinesis

IPMATIPMATCC

Julie Camp’s mitosis power point - http://sciencespot.net/Pages/classbio.html#Anchor-mitosis

http://www.youtube.com/watch?v=L0k-enzoeOM



Meiosis:Meiosis: As in mitosis, if a cell wants to make a duplicate of itself, As in mitosis, if a cell wants to make a duplicate of itself,

it first must copy its DNA (part of a chromosome).it first must copy its DNA (part of a chromosome).

Results in reproductive cells (sperm, eggs, etc). Results in reproductive cells (sperm, eggs, etc).

Part of each parent is carried to the four new cells. Part of each parent is carried to the four new cells.

MeiosisMeiosis Interphase Interphase

The cell grows and copies its DNA, and the chromatin begins to condense into chromosomes.

http://morgan.rutgers.edu/MorganWebFrames/Level1/Page7/meiosis1.html

MeiosisMeiosis Prophase Prophase II

-DNA coils tightly into chromosomes and spindle fibers appear

-In meiosis the homologous chromosomes pair with one another to form tetrads

- Portions of chromatids may break off and attach to adjacent chromatids, this process is called crossing over.


Meiosis Meiosis Metaphase IMetaphase I

- The tetrads line up - The tetrads line up randomly along the randomly along the midline of the cellmidline of the cell

-Spindle fibers attach to -Spindle fibers attach to the centromeres of the centromeres of each homologous each homologous chromosomechromosome


Meiosis Meiosis Anaphase IAnaphase I

--The chromosomes The chromosomes move to opposite move to opposite ends of the cell. ends of the cell.

- The random separation - The random separation of the homologous of the homologous chromosomes is chromosomes is called independent called independent assortmentassortment


Meiosis Meiosis Telophase I Telophase I && CytokinesisCytokinesis

The cell begins to The cell begins to divide into two divide into two daughter cells. It is daughter cells. It is important to important to understand that understand that each daughter cell each daughter cell can get any can get any combination of combination of maternal and maternal and paternal paternal chromosomes. chromosomes. http://morgan.rutgers.edu/MorganWebFrames/Level1/Page7/meiosis1.html

Meiosis Meiosis Prophase IIProphase II

Spindle fibers form and begin moving Spindle fibers form and begin moving chromosomes toward the middle of the chromosomes toward the middle of the cell cell


Meiosis Meiosis Metaphase IIMetaphase II

As in Meiosis I, the As in Meiosis I, the chromosomes line chromosomes line up on the spindle up on the spindle fibers at the fibers at the midline of the cell. midline of the cell.


Meiosis Meiosis Anaphase IIAnaphase II

The two cells each The two cells each begin to divide. As begin to divide. As in Meiosis I, the in Meiosis I, the chromosomes chromosomes move to opposite move to opposite ends of each cell. ends of each cell.


Telophase II Telophase II && CytokinesisCytokinesis

- a nuclear membrane forms around the - a nuclear membrane forms around the chromosomes in each of the four new cells. chromosomes in each of the four new cells.

- Cytokinesis II then occurs.Cytokinesis II then occurs.- - each new cell contains half the original cells - each new cell contains half the original cells

number of chromosomes number of chromosomes


http://www.youtube.com/watch?v=zGVBAHAsjJM&feature=g-vrec

http://www.youtube.com/watch?v=qCLmR9-YY7o





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Mitosis & Meiosis CHAPTER8. CHROMOSOMES Chromosome: DNA in a Eukaryotic cell that is tightly coiled and compacted in the cell nucleus Chromosome: DNA