I. The Reason for Cell Division

A. Reproduction, Growth, and Repair Unicellular organisms use division for reproduction Multicellular allow grow and development in zygotes Replace damaged or dead cells

With mitosis you get two identical cells from a parent cell Precisely replicates DNA Sends a copy of DNA to each pole of the cell Separates into two daughter cells

B. From One Cell To Two Daughter Cells The genome is your entire genetic material Some genomes of organisms are very small like prokaryotes Some are larger as in eukaryotes Division is possible because genomes are organized into chromosomes

Chromosomes are supercoils of chromatin Genes are carried on chromosomes Proteins maintain the structure and are involved in gene expression, replication, and repair

Our body cells have 46 chromosomes Our gametes contain 23 In interphase chromosomes cannot be seen During prophase and throughout mitosis chromosomes are visible

Each chromosome consist of two sister chromatids The two chromatids possess identical copies of the chromosomes DNA and are attached at the centromere

II. The Mitotic Cell Cycle

A. The Mitotic Phase Alternates With Interphase Cell division is a small portion of the cell cycle Mitosis is known as the M phase Here we have the division of the nucleus and cytokinesis

 Interphase is the nondividing stage of the cell cycle It occupies about 90% of the cell cycle It has three periods

G1 phase- 1st growth phase (the G stands for gap) S phase- synthesis phase chromosomes are duplicated G2 phase- 2nd growth phase

Mitosis is unique to eukaryotes Prokaryotes go through a process known as BINARY FISSION Mitosis is a continuous process This is a very reliable process.

Mitosis 4 phase of mitosis Prophase Metaphase Anaphase Telophase

Chromosome Sister chromatids Centromere

Prophase Centrioles split Spindle forms Chromatin coils into chromosomes. Nuclear envelope (membrane) and nucleolus disappear.

Metaphase Doubled chromosomes in middle Sister chromatids line up to separate.

Anaphase Centromere split DNA known as chromosomes again Pulled to poles Spindle shortens

Telophase Chromosomes unwind. Nuclear envelope (membrane) forms around both groups of chromosomes. Cell membrane begins to pinch together forming the cleavage furrow.

Cytokinesis Cytoplasm divided In plant cells along cell plate In animal cells at cleavage furrow

Results of Mitosis Two new daughter cells that are genetically identical to the parent. (Chromosomes are identical)

After Mitosis The cells continue to grow (interphase) and reproduce (mitosis).