The Cell Cycle(Somatic Cells)

Vocabulary

InterphaseProphaseMetaphaseAnaphase TelophaseCytokinesis

The Cell Cycle for Somatic CellsAll cells come from cells. To grow and divide (how new cells are made) cells undergo an orderly sequence of events.First, a cell must copy its DNA (in its chromosomes).The DNA copies must separate into two sides of the cell.The cell then splits into 2 identical cells. So…one skin cell divides into two skin cells, one bone cell divides into two bone cells, one muscle cell divides into two muscle cells, etc.

Mitosis:The part of the cell cycle in

which the nucleus divides to form two identical nuclei.

Interphase (occurs just before Mitosis begins)

• The cell grows in size.• DNA (in the chromatin)

and organelles (such as centrioles) are replicated (copied).

• The cell prepares for division.

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

Chromatin -(loose

threads of DNA in the

nucleus of a cell)

Interphase

Animal cell Plant cell

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

1st step in Mitosis: Prophase (preparation phase)

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

• The chromatin (duplicated DNA) coils and condenses into chromosomes.

• The nuclear membrane disappears.

• The spindle fibers begin to form.

Mitosis Prophase

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

Animal cell Plant cell

2nd step in Mitosis:metaphase (organizational phase) The chromosomes

line up in the middle of the cell.

The spindle fibers attach to the centromere of each replicated chromosome.

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

Mitosis MetaphaseAnimal cell Plant cell

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

3rd step in Mitosis: Anaphase (separation phase)

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

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

Mitosis AnaphaseAnimal cell Plant cell

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

4th step in Mitosis: Telophase

The chromosomes, along with the cytoplasm and its organelles and membranes are divided into 2 portions. This diagram shows the end of telophase.

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

Mitosis TelophaseAnimal cell Plant cell

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

After Mitosis: Cytokinesis

The actual splitting of

the daughter cells into

two separate cells is called cytokinesis

andoccurs differently in both plant and

animalCells.

Beginning of cytokinesis in a plant:

Beginning of cytokinesis in an animal:

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

Meiosis Vocabulary Diploid Cells – have pairs of similar

chromosomes.Somatic Cells – are diploid cells.Haploid Cells – do NOT have pairs of

chromosomes (have HALF the number of chromosomes that somatic cells have).

Gametes – are haploid sex cells.

Meiosis is the process of cell division that results in gametes(sex cells, sperm and egg).Gametes (haploid number of chromosomes)

are needed for sexual reproduction. In sexual reproduction, the new

organism gets half of its chromosomes from one parent (mother via the egg)and half from another parent (father via the sperm).

Before Meiosis: Interphase

The chromosomes have replicated, and the chromatin begins to condense.

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

Meiosis Prophase I• The chromosomes are

completely condensed.

• In meiosis (unlike mitosis), the homologous chromosome pairs join together.

• While the homologous chromosomes are joined, they exchange DNA (called crossing over).

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

Meiosis Metaphase I

The nuclear membrane dissolves and the homologous chromosomes attach to the spindle fibers. They are preparing to go to opposite poles.

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

Meiosis Anaphase IThe chromosomes move to opposite ends of the cell.

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

Meiosis Telophase I & Cytokinesis

The cell begins to divide into two daughter cells. It is important to understand that each daughter cell can get any combination of maternal or paternal chromosomes.

So…the daughter cells are NOT identical copies of each other (unlike mitosis).

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

Meiosis Prophase IIThe cell has divided into two daughter cells.

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

Meiosis Metaphase IIAs in Meiosis I, the chromosomes line up on the spindle fibers.

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

Meiosis Anaphase IIThe two cells each begin

to divide.The chromosomes

separate and the sister chromatids move to opposite ends of each cell.

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

Telophase II & Cytokinesis With the formation of four cells, meiosis is over. Each of these prospective germ cells carries half the number of chromosomes of somatic cells.

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

For Example:

Species Somatic Cells(diploid number results from MITOSIS)

Gametes(haploid number results from MEIOSIS)

Human 46 23

Fruit Fly 8 4

Adders-tongue fern

1440 720

This may you remember these terms:MITosis takes the cell and Makes

It Two (diploid)

Meiosis has to do with sexual reproduction

Meiosis results in an egg or sperm.

Clyde Freeman Herreid – Dept. of Biological Sciences: Buffalo State Univ. of New York

Mitosis Meiosis