CELL DIVISION / CELL REPRODUCTION
WHEN CELLS DIVIDE AND FORM 2 NEW CELLS THIS IS CALLED CELL DIVISION.
WHY DO CELLS DIVIDE?
1. IF CELL GETS TO BIG THE NUCLEUS CANNOT CONTROL WHAT GOES ON
INSIDE THE CELL.
2. IN MULTICELLUAR ORGANISMS CELL DIVIDE TO HELP THE ORGANISM GROW.
3. IN MULTICELLULAR ORGANISMS CELLS DIVIDE TO HELP REPAIR OLD AND
WORN OUT CELLS AND INJURED CELLS.
PARTS OF CELL DIVISION
3 PARTS IN CELL DIVISION
A] INTERPHASE
B] MITOSIS
C] CYTOKINESIS
A] INTERPHASE HAS 3 PARTS
1. G1 PHASE- THE CELL GOES THROUGH REGULAR CELL GROWTH
2. S PHASE � THE CELL COPIES ITS CHROMOSOMES [DNA REPLICATION]
3. G2 PHASE � THE CELL MAKES MORE CELL PARTS SO THAT THE NEW CELLS
THAT FORM WILL HAVE ENOUGH ORGANELLES.
B] MITOSIS HAS 4 MAIN PARTS
1. PROPHASE- THE NUCLEUS BREAKS DOWN, THE CHROMOSOMES, [SISTER
CHROMATIDS], GET THICKER AND THE CENTRIOLES START TO MOVE TO OPPOSITE ENDS OF THE CELL.
2. METAPHASE- THE SISTER CHROMATIDS ARE LINED UP IN THE MIDDLE OF
THE CELL, CENTRIOLES SEND OUT SPINDLE FIBERS WHICH
ATTACH TO THE SISTER CHROMATIDS AT THE
CENTROMERE.
3. ANAPHASE- SPINDLE FIBERS CONTRACT PULLING SISTER CHROMATIDS
APART FROM EACH OTHER TO OPPOSITE ENDS OF
THE CELL
4. TELOPHASE- CHROMOSOMES REACH OPPOSITE SIDES OF THE CELL, NUCLEAR MEMBRANE STARTS TO REAPPEAR, CENTRIOLES
DUPLICATE AND THE CELL MEMBRANE STARTS
TO PINCH IN TO BEGIN DIVIDING THE CYTOPLASM
C] CYTOKINESIS- LAST STEP OF CELL DIVISION THE CELL MEMBRANE
COMPLETELY DIVIDES THE CELL'S CYTOPLASM INTO TWO
IDENTICAL CELLS
MISTAKES IN THE CELL CYCLE OR CELL DIVISION
HOW DO CELL KNOW WHEN TO STOP GROWING?
1. CELL PRODUCES ENZYMES [CHEMICALS] WHICH
TELL THE NUCLEUS TO CAUSES THE CELL TO STOP GROWING.
2. CONTACT INHIBITION- THIS IS WHEN THE CELLS
KEEP GROWING UNTIL THEY TOUCH EACH OTHER. WHEN THE CELL
MEMBRANE MAKES CONTACT WITH ANOTHER CELL MEMBRANE A CHEMICAL
IS PRODUCED WHICH TELLS THE NUCLEUS TO STOP CELL GROWTH.
CANCER- IS CAUSED BY CHANGES THAT AFFECT ONE OR MORE OF THE GENES THAT CONTROL THE PRODUCTION OF ENZYMES THAT CONTROL CELL GROWTH. THE CHEMICAL TO STOP THE CELL FROM GROWING AND DIVIDING IS NOT PRODUCED AND THE CELL KEEPS GROWING AND DIVIDING FORMING A LARGE LUMP OF CELLS CALLED A TUMOR. IF ONE OF THE CELLS SEPARATE AND GOES INTO THE BLOOD STREAM IT CAN FORM NEW TUMORS WHICH CAN STOP THE FLOW OF NUTRIENTS TO TISSUES, ORGANS OR OTHER PARTS OF THE BODY CAUSING DAMAGE TO THE TISSUES OR ORGANS AND EVENTUALLY CAUSING THE DEATH OF THE ORGANISM
WHAT CAUSES THE GENES TO WORK WRONG?
CARCINOGENS � ARE SUBSTANCE OR THING THAT CAN CAUSE CANCER.
EXAMPLES OF CARCINOGENS
1. ENVIRONMENTAL FACTORS SUCH AS -CHEMICALS, POLLUTANTS, SUN-
[ULTRA VIOLET RADIATION]
2. VIRUSES- INFECTIONS FROM CERTAIN VIRUSES
BIOPSY � SAMPLE OF TISSUE THAT IS TESTED.
MALIGNANT � USED TO DESCRIBE A CANCEROUS TUMOR [MEANS THAT YOU HAVE CANCER]
BENIGN- USED TO DESCRIBE A NON CANCEROUS TUMOR
CELL DIVISION