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-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? à �

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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.

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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 Interphase AFTER Interphase

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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.

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Prophase Notes

MITOSIS

-The cell’s DNA molecules fully condense to form chromosomes. -This organism’s body cell has 4 chromosomes. -During Interphase the DNA replicated, and this is how the chromosomes can form pairs during prophase. -The nuclear membrane begins to break down.

Prophase

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Metaphase Notes

Paired chromosomes line up in the middle of the cell.

MITOSIS

Metaphase

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Anaphase Notes

Chromosome pairs are pulled apart.

MITOSIS

Anaphase

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Telophase Notes

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

MITOSIS

Telophase

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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

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Cell Cycle Interphase

Prophase

Metaphase

Anaphase

Telophase

Cytokinesis

Cell Cycle Interphase

Prophase

Metaphase

Anaphase

Telophase

Cytokinesis

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What is the result of Mitosis?

two identical cells each with the same number of chromosomes

Videos: Mitosis Cell Reproduction