Mitosis and Meiosis: Cell Division and Cancer

RECALL  THE CELL CYCLE THE SERIES OF STAGES IN THE LIFE OF A CELL  CELL DIVISION IT IS AN ESSENTIAL ASPECT OF LIFE. IT ENABLES A MULTICELLULAR ORGANISM TO GROW AND REACH THE ADULT SIZE, REPLACES WORN-OUT OR DAMAGED CELLS, AND KEEPS THE TOTAL NUMBER OF CELLS IN AN ADULT ORGANISM RELATIV...

RECALL  THE CELL CYCLE THE SERIES OF STAGES IN THE LIFE OF A CELL  CELL DIVISION IT IS AN ESSENTIAL ASPECT OF LIFE. IT ENABLES A MULTICELLULAR ORGANISM TO GROW AND REACH THE ADULT SIZE, REPLACES WORN-OUT OR DAMAGED CELLS, AND KEEPS THE TOTAL NUMBER OF CELLS IN AN ADULT ORGANISM RELATIVELY CONSTANT.  INTERPHASE IT IS THE LONGEST PHASE IN THE CELL CYCLE FOR MOST CELLS. TYPICALLY, IT LASTS FOR AT LEAST 90% OF THE TOTAL TIME REQUIRED FOR THE CELL CYCLE.  STAGES OF INTERPHASE 1. G1 (GAP 1) PHASE- 8-10 HOURS IT IS CHARACTERIZED BY AN INCREASE IN THE SUPPLY OF PROTEINS, IN THE NUMBER OF CELLULAR ORGANELLES PARTICULARLY MITOCHONDRIA AND RIBOSOMES, AND IN THE SIZE OF THE CELL. 2. S (SYNTHETIC) PHASE – 6-8 HOURS CHARACTERIZED MAINLY BY DNA SYNTHESIS OR REPLICATION. THE CELL MAKES ANOTHER COPY OF ITS CHROMOSOMES. 3. G2 (GAP 2) PHASE- 4-6 HOURS IT SPANS FROM THE COMPLETION OF DNA SYNTHESIS TO THE START OF ACTUAL CELL DIVISION.  MITOSIS The term MITOSIS is derived from the Latin word “mito” meaning “threads”. It occurs among cells during embryonic development, growth, repair of injured tissues and replacement of worn-out tissues. Certain specialized cells like nerve cells, sperm cells, and red blood cells that have no nuclei lose their power to divide. The cells which constitute the body or soma or multicellular organisms multiply by mitosis is called SOMATIC CELL DIVISION.  PHASES OF MITOSIS 1. PROPHASE – FORMATION OF MITOTIC SPINDLE FIBERS. The nuclear membrane disappears The nucleoli disappear A pair of centrioles moves to form each pole and the mitotic spindle forms between the poles (centrioles) And the replicated DNA begins to condense into distinctive chromosomes.  PHASES OF MITOSIS 2. METAPHASE: ALIGNMENT OF CHROMOSOMES Characterized by the alignment of the chromosomes along the EQUATORIAL PLATE of the cell.  PHASES OF MITOSIS 3. ANAPHASE: MOVEMENT OF THE DAUGHTER CHROMOSOMES Characterized by the separation of the chromosomes and the movement each of the replicated chromosomes toward opposite poles.  PHASES OF MITOSIS 4. TELOPHASE: FORMATION OF TWO DAUGHTER NUCLEI Daughter chromosomes reach the opposite end of the poles. This stage is characterized by the formation of a nuclear envelope around each set of the chromosomes. The chromosomes uncoil, and once again appear thread-like. Nucleoli reappear. The mitotic spindle fiber disappear and the equal division of one nucleus into two identical daughter nuclei is completed. PHASES OF MITOSIS 5. CYTOKINESIS: DIVISION OF THE CYTOPLASM Final phase and characterized mainly by the division of the cytoplasm. In plant cells, cellulose deposits accumulate along the equator, forming a structure called “cell plate” from which the cell wall forms. A new plasma membrane extends across both sides of the cell plate. In animal cells, the cytoplasm divides by the formation of a groove called “cleavage furrow”. PHASES OF MITOSIS I- I P- RAY M-ORE A-T T-HE C-HURCH CANCER  CANCER CELLS: GROWING OUT OF CONTROL THE SUQUENTIAL EVENTS OF THE CELL CYCLE ARE DIRECTED BY A CELL CYCLE CONTROL SYSTEM THAT CONSISTS OF SPECIALIZED PROTEINS WITHIN THE CELL. THESE PROTEINS INTEGRATE INFORMATION FROM THE ENVIRONMENT AND FROM THE OTHER BODY CELLS AND SEND “STOP” AND “GO-AHEAD” SIGNAL AT A CERTAIN KEY POINTS.  CANCER CELLS: GROWING OUT OF CONTROL The abnormal behavior of cancer cells begins when a single cell undergoes transformation, a process whereby a normal cell converts to a cancer cell. Transformation occurs after a genetic change (mutation) in one or more genes that encode for proteins in the cell cycle control system.  BENIGN TUMOR Because a transformed cell grows abnormally, the immune system normally recognizes and destroys it. However, if the cell, evades destruction, it may proliferate to form a TUMOR, an abnormally growing mass of the body cells. If the abnormal cells remain at the original site, the lump is called benign tumor. Benign tumors can cause problems if they grow larger and disrupt certain organs, such as brain but they can be removed by surgery. MALIGNANT TUMOR It can spread into neighboring tissues and other parts of the body, displacing normal tissues and interrupting organ function. Causes cancer. Cancer cells may separate from the original tumor or secrete signal molecule that cause blood vessels to grow toward the tumor. The spread of cancer cells beyond their original site is called METASTASIS. CANCER TREATMENT THE THREE (3) MAIN TYPES OF CANCER TREATMENT ARE SOMETIMES REFERRED TO AS “SLASH, BURN, AND POISON”. SLASH- SURGERY TO REMOVE A TUMOR. BURN- RADIATION THERAPY ❑ PARTS OF THE BODY THAT HAVE CANCEROUS TUMORS ARE EXPOSED TO CONCENTRATED BEAMS OF HIGH-ENERGY RADIATION. (SIDE EFFECTS: NAUSEA AND HAIR LOSS) POISON- CHEMOTHERAPY ❑ DRUGS ARE ADMINISTERED THAT DISRUPT CELL DIVISION.  CANCER CELLS videos\CANCER CELL 1ST.mp4 videos\CANCER CELL.mp4 MEIOSIS  Characteristics of MEIOSIS 1. It results in daughter cells having the number of chromosomes (haploid number) of the parent cell. 2. The resulting daughter cells in meiosis are not alike. They do not have the same exact copies of chromosomes. 3. Produces four (4) daughter cells. 4. Occurs only in reproductive cells of ovaries and testes.  MEIOSIS In humans, each body (somatic) cell contains two sets of chromosomes, with 23 chromosomes in each set. Each of the 23 pairs is called homologous pair. ONE set comes from each parent cell.  DIPLOID CELL- a cell that contains two complete sets or homologous pairs of chromosomes. DIPLOID NUMBER- the number of chromosomes in a diploid cell. Represent by “2N”. HAPLOID CELL – a cell containing a single set of chromosomes. Human sex cells (egg and sperm) contain only half the number of chromosomes found in the body cells. N (23) FERTILIZATION- a haploid sperm cell fuses with a haploid egg cell, results in a fertilized egg, called a ZYGOTE which is DIPLOID. PHASES OF MEIOSIS I PROPHASE I ❑ Chromosomes become thick and visible. ❑ Chromosomes of each homologous pair are tangled together. ❑ Each pair consists of a total of four chromatids, because each chromosomes in the pair had replicated before meiosis began. ❑ CROSSING OVER- is the exchange of genes between pairs of homologous chromosomes. PHASES OF MEIOSIS I 2. METAPHASE I ❑ The homologous chromosomes are still together. ❑ The pairs of chromosomes are arranged in the middle of the cell. PHASES OF MEIOSIS I 3. ANAPHASE I ❑ The homologous pairs of chromosomes separate from each other during anaphase I. ❑ Spindle fibers pull members from each pair of chromosomes to opposite ends of the cell. ❑ Notice that each individual chromosomes still consist of two sister chromatids. PHASES OF MEIOSIS I 4. TELOPHASE I ❑ Depending on the type of organism, a new nuclear envelope may or may not form during telophase. In either case, cytokinesis takes place during telophase. ❑ After cytokinesis, each new cell is haploid, containing one chromosome from each pair.  MEIOSIS II Recall that, before meiosis began, each chromosome replicated to become two sister chromatids. Each of the daughter cells produced during meiosis I divides again during meiosis II. Meiosis II is just a typical Mitosis but produces a four haploid daughter cells.  Klinefelter syndrome – XXY Turner’s Syndrome – X Triple X syndrome – XXX Edward Syndrome – Trisomy 18 XYY  EDWARD MORDRAKE \Edward Mordake (variously Mordrake) is the apocryphal subject of an urban legend who was, according to the legend, born in the 19th century, heir to an English peerage, and had an extra face on the back of his head. The duplicate face could not see, eat or speak out loud but was said to "sneer while Mordake was happy" and "smile while Mordake was weeping". Mordake repeatedly begged doctors to have his "demon face" removed, claiming that it whispered things that "one would only speak about in hell" at night, but no doctor would attempt it. According to the legend, Mordake committed suicide at the age of 23.