Ch 5 and 6.1 and 6.2 Cell Division

Cell Reproduction Mitosis Meiosis Creates 2 Creates 4 identical cells different cells Creates body cells Creates sex cells Diploid cells = 2n or 2 sets of chromosomes Haploid cells = 1n or 1 set of chromosomes Body cells, Skin Cells, Tissues, Organs Sperm and egg

Mitosis Why do cells reproduce? GROWTH REPAIR Increase in number of cells. GROWTH ____________________ Replace worn out or damaged cells. REPAIR ____________________

Life Spans of Body Cells

The cell cycle has four main stages. 1. Gap 1: Cell Growth 2. Synthesis: DNA Replication 3. Gap 2: Preparation of Mitosis 4. Mitosis Interphase – A long period of cell growth

G1 Phase: The cell grows in size. Checkpoint 1 S Phase: DNA # is doubled. Checkpoint 2 G2 Phase: gets ready for mitosis. Develops its organelles. *Has 2 complete sets of DNA

Interphase G1 phase: Cell Growth S phase: DNA Replication

Duplicated Chromosome = Sister chromatids 1 Chromosome = 1 chromatid Duplicated Chromosome = Sister chromatids

Condensed, duplicated chromosome or sister chromatids centromere Condensed, duplicated chromosome or sister chromatids Holds the duplicated chromosome together G2 phase: Cell gets ready for mitosis

***DNA is in the form of Chromatin (ball of DNA) INTERPHASE ***DNA is in the form of Chromatin (ball of DNA) Centrioles copies are made 1. More cytoplasm- cell grows. 2. DNA is being replicated. 3. More organelles The cell is getting ready for MITOSIS, cell division.

_______________________________________ Steps of Mitosis Prophase Metaphase Anaphase Telophase _______________________________________ PMAT

X 3. Centrioles move apart. 2. Nuclear Membrane Breaks down Mitosis – PROPHASE 4. Fibers form 3. Centrioles move apart. X 1.Chromatin forms visible chromosomes 2. Nuclear Membrane Breaks down

PROPHASE 1. DNA 2. Nuclear Membrane 3. Centrioles 4. Fibers Move apart from one another in opposite directions Begins to break down Form between centrioles Chromatin condenses into visible chromosomes

4.THE NUCLEAR MEMBRANE IS NO LONGER PRESENT 2. Spindle fibers connect to the sister chromatids Mitosis – Metaphase 4.THE NUCLEAR MEMBRANE IS NO LONGER PRESENT X 3. Sister chromatids are lined up along the middle of the cell. 1. Centrioles move to opposite poles.

METAPHASE 1. Centrioles 2. Fibers 3. DNA 4. Nuclear Membrane Sister chromatids are pulled to the middle of the cell Continue to move to opposite ends of the cell Attach to the sister chromatids. Is completely gone

Mitosis – ANAPHASE 2.Centrioles begin to pull the chromosomes toward the opposite sides of the cell. > 1. Sister Chromatids separate

ANAPHASE 1.Sister Chromatids 2.Fibers 3.Centrioles 4.Nuclear Membrane Pulled apart Each chromatid is separate from its “sister” Still at opposite sides of the cell Pull each chromatid toward opposite ends of cell Is still gone

> 2. Nuclear Membrane begins to reappear Mitosis – TELOPHASE > 2. Nuclear Membrane begins to reappear 3.Cell Membrane pinches at center 4. Fibers begin to disappear 1.Chromosomes are at opposite sides of the cell

TELOPHASE 1.Sister Chromatids 2.Nuclear Membrane 3.Cell Membrane 4.Fibers Each end of cell has a complete set of chromosomes. Begins to pinch at the center, forming two new identical cells Begin to disappear Begins to reform around the sets of chromosomes

Cell Membrane splits into two new identical cells CYTOKINESIS Cell Membrane splits into two new identical cells

METAPHASE PROPHASE TELOPHASE ANAPHASE Cytokinesis

ANAPHASE METAPHASE TELOPHASE PROPHASE Phases of Mitosis: Prophase

So What Does The Process of Mitosis Look Like? Another Animation Control of the cell cycle Cell Cycle of Mitosis Interactive review of mitosis from Classzone.com Video clips

Plant Cell vs. Animal Cell MITOSIS Plant Cell vs. Animal Cell The process is VERY SIMILAR in each type of cell. There are only 2 differences: Plant cells do not have centrioles The cell membrane cannot pinch because of the cell wall. Instead a cell plate forms between the 2 nuclei division.

Changes in the Rate of Mitosis Changes often occur in the growth rate of cells. Faster Rate of Mitosis: CANCER _______________________ Slower Rate of Mitosis: AGING _______________________

Regulation of the Cell Cycle External factors Physical signal – cell to cell contact. Once a cell touches another cell it stops dividing. When cells fail to respond to the external signal, the cells continue to divide uncontrollably and form clumps. Tumor – is a clump of cancer cells. Benign – tumor is harmless, the cells are clustered together tightly and can be removed. Malignant – tumor is bad, the cells can break away and be carried to other parts of the body. When a tumor has metastasized, it means the cancer cells have spread to other parts of the body.

Why are tumors Harmful? Cancer cells do not perform the specialized functions needed by the body. In the lung – cancer cells do not exchange oxygen and carbon dioxide. In the brain – they do not transmit the messages needed to interpret information to the body Can exert great pressure on surrounding organs.

Cancer 1. CHEMICALS Chemicals used on household items Drugs Carcinogen – a substance known to produce or promote the development of cancer cells. 1. CHEMICALS Chemicals used on household items and/or pesticides, tobacco Drugs Nuclear Wastes 2. RADIATION 3. SOME VIRUSES HPV Sun X-Rays

cancer cell bloodstream normal cell

Meiosis (cell reproduction) Cuts chromosome number in half. Creates haploid cells. Creates sperm and egg Spermatogenesis – the creation of sperm Oogenesis – the creation of ova (egg) Meiosis (cell reproduction)

Sperm or Eggs In males: These cells develop into 4 individual sperm that are genetically different from the parent cell. In females: These cells would have developed into 3 small polar bodies which will die and only 1 large egg. (THIS IS DUE TO AN UNEVEN DIVISION OF CYTOPLASM DURING MEIOSIS)

Fertilization: Union of sperm and Egg Creates a zygote Re-establishes the full number of chromosomes 2 chromosomes 2 chromosomes 4 chromosomes 32

Mitosis vs. Meiosis To make sperm and eggs with Occurs in sex cells For growth and to replace old, worn out cells. Occurs in body cells Two cells from 1 cell Identical cells to the parent cell. Same number of chromosomes as the original (2N) - diploid One division of the nucleus. To make sperm and eggs with Occurs in sex cells Four cells from 1 cell Genetically different from the parent cell. Half the number of chromosomes (1N) - haploid Two divisions of the nucleus. 33