Cell DivisionCell Division

How do we get new cells and new living

things?

Cell Division

MitosisMitosis• Mitosis, the process

by which the body grows and replaces cells, is divided into five phases.

Meiosis• Meiosis occurs during

the formation of gametes in animalsin animals.

Interphase

Prophase

Metaphase

Anaphase

Telophase

Interphase

MitosisMitosisOverviewOverview

MitosisMitosisOverviewOverview

Interphase• G1 phase- Cell growth

• S phase- DNA Replication

• G2 phase- Preparation for mitosis

• This is the longest phase of all

Prophase

• Nucleus Condenses

• DNA is compacted into movable packages called Chromosomes

Metaphase

• Aligning chromosomes at cell equator

• Attaching spindle fibers from each new daughter cell pole to each chromosome at the centromere

Anaphase

• Spindle fibers pull chromosomes apart • Half of the chromosomes (chromatid)

moves to a new daughter cell

Telophase & Cytokinesis

• DNA gathers and two nuclei form • new cell wall and membrane appears between

the two nuclei to form two new daughter cells and cytoplasm pinches in half

Cell PlateCell Plate

Interphase

• From new cell formation into rest phase again

MeiosisMeiosisMeiosisMeiosis

Gamete Formation and Recombination

Meiosis Definition

cell division that produces reproductive cells in sexually reproducing organisms; the nucleus divides into four nuclei each containing half the chromosome number leading to gametes.

Division 1

• Interphase 1: DNA replication• Prophase 1: Each chromosome forms and

remains closely associated. These are called sister chromatids.

• Metaphase 1: Homologous chromosomes align at the equatorial plate.

• Anaphase 1: Homologous pairs separate with sister chromatids remaining together.

• Telophase 1: Two daughter cells are formed with each daughter containing only one chromosome of the homologous pair.

Division 2

• Prophase 2: DNA does not replicate.

• Metaphase 2: Chromosomes align at the equatorial plate.

• Anaphase 2: Centromeres divide and sister chromatids migrate separately to each pole.

• Telophase 2: Cell division is complete. Four haploid daughter cells are obtained.

http://www.sumanasinc.com/webcontent/anisamples/majorsbiology/meiosis.html

Web Link to animated Meiosis

Who can Explain Each Step?

Step 1 Step 2

Step 3

Step 4