6/1/2016 CHAPTER 8 MITOSIS

6/1/2016 MITOSIS Cell division is essential to: Cell division is essential to: Replace dead cells (50 million cells die per second) Replace dead cells (50 million cells die per second) Repair damaged tissues Repair damaged tissues Growth Growth Maintain the body Maintain the body Cell division includes two main events: Cell division includes two main events: Mitosis – division of nucleus and DNA Mitosis – division of nucleus and DNA Cytokinesis – division of the cytoplasm and organelles Cytokinesis – division of the cytoplasm and organelles

6/1/2016 THE CELL CYCLE Most cells go through the same cell cycle Most cells go through the same cell cycle Time at each stage varies Time at each stage varies 5 stages to life cycle of a cell, but is a continuous process 5 stages to life cycle of a cell, but is a continuous process The five stages are: The five stages are: G1 — gap (growth) phase one G1 — gap (growth) phase one S — synthesis S — synthesis G2 — gap (growth) phase two G2 — gap (growth) phase two Cell division (mitosis and cytokinesis) Cell division (mitosis and cytokinesis) G0 — gap (growth) mitotic dormancy G0 — gap (growth) mitotic dormancy

6/1/2016 THE CELL CYCLE

6/1/2016 THE CELL CYCLE G0 phase – cells are not dividing, they are differentiated or specialized in their function G0 phase – cells are not dividing, they are differentiated or specialized in their function Some cells remain in the G0 phase (nerve cells) Some cells remain in the G0 phase (nerve cells) Others can proceed back into the growth cycle (G1, S, and G2) – bone cells Others can proceed back into the growth cycle (G1, S, and G2) – bone cells G1, S, and G2, occur during the stage called interphase. G1, S, and G2, occur during the stage called interphase.

6/1/2016 THE CELL CYCLE G1 phase – cell growth, manufacture of tRNA, mRNA, ribosomes, enzymes, other cell components G1 phase – cell growth, manufacture of tRNA, mRNA, ribosomes, enzymes, other cell components S phase – a new DNA strand is synthesized S phase – a new DNA strand is synthesized G2 phase – the cell prepares to go through mitosis G2 phase – the cell prepares to go through mitosis During interphase, cells are engaging in various metabolic activities such as: During interphase, cells are engaging in various metabolic activities such as: Photosynthesis Photosynthesis muscle cell contractions muscle cell contractions glandular-cell secretion glandular-cell secretion

6/1/2016 A CELL DURING INTERPHASE

6/1/2016 After interphase, the chromosomes consist of two strands known as sister chromatids

6/1/2016 STAGES OF MITOSIS The stages of mitosis are: The stages of mitosis are: Prophase Prophase Metaphase Metaphase Anaphase Anaphase Telophase Telophase

6/1/2016 PROPHASE First stage of mitosis First stage of mitosis Individual chromosomes become visible. Individual chromosomes become visible. Nuclear membrane begins to disappear. Nuclear membrane begins to disappear. Spindles begin to form. Spindles begin to form. Two identical chromatids are attached by the centromere. Two identical chromatids are attached by the centromere. Centrioles move to opposite poles. Centrioles move to opposite poles.

6/1/2016 A CELL DURING EARLY PROPHASE

6/1/2016 A CELL DURING LATE PROPHASE

6/1/2016METAPHASE Second stage of mitosis Second stage of mitosis Nuclear membrane has disappeared Nuclear membrane has disappeared Centrioles are at opposite poles Centrioles are at opposite poles Chromosomes are aligned at equatorial plane (middle of cell) Chromosomes are aligned at equatorial plane (middle of cell) Each chromosome still has two chromatids Each chromosome still has two chromatids human cells have 46 chromosomes, each with two chromatids (total of 92 chromatids) human cells have 46 chromosomes, each with two chromatids (total of 92 chromatids) Chromosomes are attached to the spindle Chromosomes are attached to the spindle

6/1/2016 A CELL DURING METAPHASE

6/1/2016 ANAPHASE Third stage of mitosis Third stage of mitosis Centromeres split and chromatids (daughter chromosomes) separate Centromeres split and chromatids (daughter chromosomes) separate Chromatids are pulled to opposite poles by the spindle which attaches to a protein (kinetochore) at the centromere Chromatids are pulled to opposite poles by the spindle which attaches to a protein (kinetochore) at the centromere Each chromatid is the exact copy of the other Each chromatid is the exact copy of the other

6/1/2016 A CELL DURING ANAPHASE

6/1/2016 TELOPHASE Last stage of mitosis Last stage of mitosis Cytokinesis (division of the cytoplasm) takes place Cytokinesis (division of the cytoplasm) takes place Chromosomes unwind Chromosomes unwind Nuclear membrane reappears enclosing the chromosomes Nuclear membrane reappears enclosing the chromosomes Nucleoli reappear Nucleoli reappear Each daughter cell now enters G1 stage of interphase Each daughter cell now enters G1 stage of interphase Cells grow and enter another cycle of mitosis. Cells grow and enter another cycle of mitosis.

6/1/2016 TELOPHASE/CYTOKINESIS TELOPHASE/CYTOKINESIS

6/1/2016 MITOSIS IN ANIMAL CELLS

6/1/2016 PLANT AND ANIMAL CELL DIFFERENCES Animal and plant cells have very similar cell division cycles Animal and plant cells have very similar cell division cycles Differences include: Differences include: Plant cells do not have centrioles, but are still capable of producing a spindle Plant cells do not have centrioles, but are still capable of producing a spindle During cytokinesis, animal cells form a cleavage furrow, plant cells form a cell plate which becomes the cell wall. During cytokinesis, animal cells form a cleavage furrow, plant cells form a cell plate which becomes the cell wall.

6/1/2016 COMPARISON OF ANIMAL AND PLANT MITOSIS

6/1/2016 COMPARISON OF ANIMAL AND PLANT MITOSIS

6/1/2016 PLANT AND ANIMAL CELL DIFFERENCES

6/1/2016 DIFFERENTIATION Even though all cells originate from a single fertilized egg, they are not the same Even though all cells originate from a single fertilized egg, they are not the same All cells are genetically identical but have different functions All cells are genetically identical but have different functions nerve cells nerve cells muscle cells muscle cells red blood cells... each with a specific function red blood cells... each with a specific function The process of creating these specialized cells is called cell differentiation The process of creating these specialized cells is called cell differentiation

6/1/2016 STEM CELLS Cells that can become any cell type Cells that can become any cell type Stem cells in the bone marrow can be differentiated and become a red or white blood cell Stem cells in the bone marrow can be differentiated and become a red or white blood cell Bone marrow transplants are successful for treating certain diseases because the stem cells can differentiate to the desired cells Bone marrow transplants are successful for treating certain diseases because the stem cells can differentiate to the desired cells Other sources include embryonic stems cells and umbilical cord stem cells Other sources include embryonic stems cells and umbilical cord stem cells Both sources could potentially be used to produce nerve, liver, muscle, skin, or brain cells Both sources could potentially be used to produce nerve, liver, muscle, skin, or brain cells

6/1/2016 ABNORMAL CELL DIVISION Cells that have lost their ability to stop dividing are known as cancerous cells or tumors. Cells that have lost their ability to stop dividing are known as cancerous cells or tumors. Benign tumor – stays in one location Benign tumor – stays in one location Malignant tumor – can spread and invade other parts of the body Malignant tumor – can spread and invade other parts of the body Uncontrolled cell division in white blood cells causes leukemia. Uncontrolled cell division in white blood cells causes leukemia. Cancer can be caused by carcinogens. Cancer can be caused by carcinogens. Some cancers can be treated through surgery. Some cancers can be treated through surgery. Other treatments include chemotherapy and radiation. Other treatments include chemotherapy and radiation.

6/1/2016 ABNORMAL CELL DIVISION Chemotherapy uses a combination of chemicals to destroy cancer cells. Chemotherapy uses a combination of chemicals to destroy cancer cells. Side effects include susceptibility to infections, hair loss, and intestinal disorders Side effects include susceptibility to infections, hair loss, and intestinal disorders Radiation uses X rays or gamma rays that disrupt the DNA structure of cancer cells Radiation uses X rays or gamma rays that disrupt the DNA structure of cancer cells Causes the cells to commit “suicide” (apoptosis) Causes the cells to commit “suicide” (apoptosis) Side effects include hair loss, bloody vomiting and diarrhea, reduced white blood cell count Side effects include hair loss, bloody vomiting and diarrhea, reduced white blood cell count

6/1/2016 CHAPTER 8 MITOSIS

6/1/2016

After interphase, the chromosomes consist of two strands known as sister chromatids

6/1/2016

MITOSIS IN ANIMAL CELLS

6/1/2016

COMPARISON OF ANIMAL AND PLANT MITOSIS

6/1/2016

PLANT AND ANIMAL CELL DIFFERENCES

6/1/2016