CELL REPRODUCTION Chapter 8 Video: Cell Division (19)

“CELLS ARE COMING FROM OTHER CELLS” (Virchow, Cell Theory) CELL DIVISION: It is the process by which new cells are produced from one cell and they are identical to the original one. (In this moment as you are reading this, millions of your cells are growing, dividing and dying)

All living things have CHROMOSOMES. CHROMOSOMES: Structures made of DNA that contain the genetic material. There are 46 in each human body cell. They are in the Nucleus (or cytoplasm). DNA must be copied in cell reproduction.

Most of the cell’s lifetime, chromosomes are in the shape of CHROMATIN (long strands of DNA wrapped without order around Proteins, in the nucleus)

Before the cell divides, the CHROMATIN is organized in the shape of CHROMOSOMES. Each chromosome is made of 2 SISTER CHROMATIDS.

CELL CYCLE G1 + S + G2= INTERPHASE (Preparation for Mitosis)

INTERPHASE The cell spends most of the time in this phase G1: Cells grow in size S: DNA is copied G2: The cell gets ready for division (Mitosis) They have CHROMATIN They have 2 CENTRIOLES They have NUCLEAR ENVELOPE

MITOSIS Mitosis has 4 phases: PROPHASE METAPHASE ANAPHASE TELOPHASE Video: Biologix: Cell Cycle Mitosis and Cytoplasmic Division (29)

PROPHASE First and longest phase of Mitosis First and longest phase of Mitosis The chromatin is organized into visible chromosomes The chromatin is organized into visible chromosomes Nuclear envelope and nucleolus disappeared Nuclear envelope and nucleolus disappeared In animal cells, the CENTRIOLES migrate to the opposite ends of the cell and the SPINDLE FIBERS begin to form In animal cells, the CENTRIOLES migrate to the opposite ends of the cell and the SPINDLE FIBERS begin to form In plant cells, the SPINDLES FIBERS form without centrioles. In plant cells, the SPINDLES FIBERS form without centrioles.

METAPHASE Short phase Short phase The chromosomes lined up in the middle of the SPINDLE FIBERS by their CENTROMERES. The chromosomes lined up in the middle of the SPINDLE FIBERS by their CENTROMERES.

ANAPHASE Complete separation of homologous chromosomes. Complete separation of homologous chromosomes. The chromosomes are pulled apart by the SPINDLE FIBERS. The chromosomes are pulled apart by the SPINDLE FIBERS. The chromosomes The chromosomes separate completely to the opposite sides of the cell.

TELOPHASE Final phase of Mitosis Final phase of Mitosis The chromosomes unwind again (CHROMATIN) The chromosomes unwind again (CHROMATIN) The SPINDLE FIBERS begin to break down The SPINDLE FIBERS begin to break down Nucleolus reappears Nucleolus reappears New NUCLEAR ENVELOPE reappears New NUCLEAR ENVELOPE reappears New CELL MEMBRANE forms around the new cells New CELL MEMBRANE forms around the new cells

CYTOKINESIS Division of the cytoplasm after MITOSIS. Division of the cytoplasm after MITOSIS. Animal cells (contractile Ring that divides the cytoplasm) Plant cells (form a CELL PLATE between The cells)

RESULT OF MITOSIS From ONE original cell 2 DAUGHTER CELLS result that are identical to the parent cell.

MEIOSIS

WHY MEIOSIS? Process of cell division in which one cell produces 4 daughter cells with HALF the chromosomes than the original one. The daughter cells are called The daughter cells are called GAMETES (eggs, sperm)

TESTICULESSPERM OVARIES ZYGOTE Mitosis EGGS

Human body cells have 46 chromosomes. They are in pairs that contain information for the same traits: HOMOLOGOUS CHROMOSOMES. Cells with 2 sets of chromosomes are called DIPLOID (2n) Human sex cells (sperm and eggs) have 23 chromosomes. They do not have homologous chromosomes. HAPLOID (n)

Before Meiosis… INTERPHASE DNA and CENTRIOLES duplicate DNA and CENTRIOLES duplicate Cells grow to its maximum size Cells grow to its maximum size Chromatin changes into HOMOLOGOUS CHROMOSOMES Chromatin changes into HOMOLOGOUS CHROMOSOMES

MEIOSIS (1 cell 2 cells with the same number of the chromosomes of the parent cell) MEIOSIS I (1 cell 2 cells with the same number of the chromosomes of the parent cell) PROPHASE I Chromatin forms homologous chromosomes Chromatin forms homologous chromosomes Nucleolus and nuclear envelope disappear Nucleolus and nuclear envelope disappear Spindle fibers are formed from the centrioles Spindle fibers are formed from the centrioles CROSSING OVER takes place CROSSING OVER takes place

: Exchange of genetic information between pairs of homologous chromosomes. CROSSING OVER : Exchange of genetic information between pairs of homologous chromosomes.

METAPHASE I The homologous chromosomes line up in the middle of the cell by the The homologous chromosomes line up in the middle of the cell by the spindle fibers. spindle fibers. ANAPHASE I The homologous chromosomes separate from each other. The homologous chromosomes separate from each other.

TELOPHASE I Nuclear envelope and nucleolus reappear Nuclear envelope and nucleolus reappear 2 cells begin to form 2 cells begin to form Spindle fibers begin to Spindle fibers begin todisappear CYTOKINESIS I Cytoplasm divides forming 2 new cells with the same number of chromosomes as the original cell. Cytoplasm divides forming 2 new cells with the same number of chromosomes as the original cell.

(2 cell 4 cells with half of the chromosomes of the parent cell) MEIOSIS II (2 cell 4 cells with half of the chromosomes of the parent cell) PROPHASE II Sister chromatids are together Sister chromatids are together Nucleolus and nuclear envelope disappear Nucleolus and nuclear envelope disappear Spindle fibers are formed from the centrioles Spindle fibers are formed from the centrioles

METAPHASE II The sister chromatids line up in The sister chromatids line up in the middle of the cell by the middle of the cell by spindle fibers. ANAPHASE II The sister chromatids The sister chromatids separate from each other.

TELOPHASE II Nuclear envelope and nucleolus reappear Nuclear envelope and nucleolus reappear 4 cells begin to form 4 cells begin to form Spindle fibers begin to disappear Spindle fibers begin to disappear CYTOKINESIS II Cytoplasm divides forming Cytoplasm divides forming 4 new cells with half of the chromosomes of the original one.

MITOSIS: CHROMOSOMES MEIOSIS I: HOMOLOGOUS CHROMOSOMES MEIOSIS II: SISTER CHROMATIDS

MITOSI S MEIOSI S NUMBER OF CELLS AT THE END 24 NUMBER OF CHROMOSOMES AT THE END The same amount than the parent cell Half of the chromosome s of the parent cell TYPE OF CELLS Any body cellOnly sex cells

CANCER If the cell cycle goes out of control. Normal cells with damaged genes. CANCER

Cancer cells keep dividing and form clumps called TUMORS. A BENIGN TUMOR is harmless because the cells stay together and can be removed A MALIGNANT TUMOR can be lethal and has cancer cells that break away from the tumor and travel to other parts of the body () A MALIGNANT TUMOR can be lethal and has cancer cells that break away from the tumor and travel to other parts of the body (METASTASIS)

CAUSES OF CANCER: Genetics Genetics External factors: Sunlight External factors: SunlightSmoke/Drugs/AlcoholPollutionX-Rays Bad nutrition (obesity) Stress

CANCER FACTS Cancer may affect people at any age. Cancer may affect people at any age. Cancer causes about 13% of all deaths in the world. Cancer causes about 13% of all deaths in the world. Cancer can affect all animals. Most cancers can be treated and some cured using radiotherapy, chemotherapy or surgery. Most cancers can be treated and some cured using radiotherapy, chemotherapy or surgery. Video: Life Science: Cells (20) Video: Life Science: Cells (20) WS: Mitosis & Meiosis WS: Mitosis & Meiosis