-This week we are talking about how cells reproduce… Next week we will talk about how organisms reproduce… Why Do Cells Need to Reproduce? -Growth, Repair, Replacement Cells divide whenever a tissue / organ / organism is growing or needs repair. -What is the result of cell reproduction? A cell divides into two cells by making a copy of itself. The result is two genetically identical cells. -Cell Division = Cell Reproduction (this can be confusing!)

Mitosis Mitosis is part of a cell’s life cycle. Cell division occurs during the stage of Mitosis. During this stage, new cells with identical genetic information are formed. The genetic material and cytoplasm are equally divided between two cells. What is the genetic material? 

Chromosomes are structures located in the nucleus of the cell. Chromosomes are made of DNA and protein. Chromosomes contain genes.

Genes control the physical characteristics of a species. All the genes of an organism make up the organism’s genome. All organisms of the same species contain the same number of chromosomes in their nuclei.

The Cell Cycle All cells develop from existing cells. This enables multicellular organisms to grow, replace dead cells, and reproduce. A cell’s life can be described with the cell cycle. There are three stages of the cell cycle: –Interphase –Cell Division (mitosis or meiosis) –Cytokinesis

Interphase (occurs before mitosis begins) Three Parts of Interphase: G1 phase: The cell is growing and performing its day to day functions. S phase: The cell replicates its DNA. G2 phase: The cell is preparing for cell division. Main Point of Interphase: DNA (chromosomes) are copied (# doubles) BEFORE InterphaseAFTER Interphase

What Interphase looks like under the microscope: Distinct nucleus. You should be able to easily distinguish the nucleus from the cytoplasm. Chromatin DNA. Chromosomes are yet fully condensed, this is called chromatin. Because chromatin is very thin, you can not see individual DNA strands. There are indistinct swirls of chromatin dispersed throughout the nucleus.

ProphaseNotes MITOSIS -The cell’s DNA molecules fully condense to form chromosomes. -This organism’s body cell has 4 chromosomes. -The nuclear membrane begins to break down.

Prophase

MetaphaseNotes -Paired chromosomes line up in the middle of the cell. -Nuclear membrane is completely gone. MITOSIS

Metaphase

AnaphaseNotes Chromosome pairs are pulled apart. MITOSIS

Anaphase

TelophaseNotes A nuclear membrane forms around each set of the separated chromosomes (chromatin). MITOSIS

Telophase

Cytokinesis (the stage after mitosis) Notes After mitosis, there are two cells with 4 chromosomes (chromatin) in each cell. During cytokinesis, the cell membrane forms around the two identical cells.

Cytokinesis

Cell Cycle Interphase Prophase Metaphase Anaphase Telophase Cytokinesis

Cell Cycle Interphase Prophase Metaphase Anaphase Telophase Cytokinesis

What is the result of Mitosis? two identical cells each with the same number of chromosomes Videos: Mitosis Cell Reproduction