Mitosis and Cell Division

Three reasons why cells reproduce by asexual reproduction: 1. Growth 2 Three reasons why cells reproduce by asexual reproduction: 1. Growth 2. Repair 3. Replacement Skin cancer - the abnormal growth of skin cells - most often develops on skin exposed to the sun. Cell that reproduce by asexual reproduction reproduce constantly.

Cell division All complex organisms originated from a single fertilized egg. Every cell in your body started here, through cell division the numbers are increased Cell then specialise and change into their various roles

Parent cell Chromosomes are copied and double in number Chromosomes now split 2 daughter cells identical to original

Mitosis All daughter cells contain the same genetic information from the original parent cell from which it was copied. Every different type cell in your body contains the same genes, but only some act to make the cells specialise – e.g. into nerve or muscle tissue.

Stages of Cell Division 1. Interphase 2. Mitosis Prophase Metaphase Anaphase Telophase 3. Cytokinesis

Interphase 1. DNA replication 2. Centrioles duplicate (animal cells only)

Prophase Chromatin condenses into double stranded chromosomes joined by a centromere Nuclear membrane dissolves freeing the DNA Spindle fibers stretch across the cell from centrioles that have moved to opposite ends of the cell

Metaphase Tugging action of the spindle fibers pulls the double stranded chromosomes into a line across the middle of the cell Highly organized so that both new cells will get exactly the same DNA

Anaphase Spindle fibers begin to contract and shorten This action pulls the centomere apart, allowing one of each of the replicated chromosomes to move to opposite ends (poles) of the cell.

Telophase One complete set of chromosomes is now at each pole of the cell Nuclear membrane forms around each set of chromosomes Chromosomes uncoil into chromatin Cytokinesis begins

Cytokinesis Division of all the rest of the cell’s organelles into two identical daughter cells. Animal Cells: A cleavage furrow pinches off the cell. Plants Cells: A cell plate develops across the centre of the cell, forming a new cell wall

Mitosis – animal bone cells 2 1 Cells split Chromosomes copied Parent cell 3 4 5 2 daughter cells Copies separating

Plants apical meristem

Rat – epithelial cells

Cancer … cell cycle gone wrong What is cancer? Cancer is essentially a disease of mitosis The normal 'checkpoints' regulating mitosis are ignored or overridden by the cancer cell. Cancer begins when a normal single cell is transformed into a cancer cell. Often this is because of a DNA mutation that occurs in one of the genes that normally controls growth. Once these crucial Cell Cycle genes start behaving abnormally, cancer cells start to proliferate wildly by repeated, uncontrolled mitosis

Cancer Growth Animation Worksheet View the cancer growth animation using the following url: http://www.pbs.org/wgbh/nova/cancer/grow_flash.html Answer the following questions from the animation 1. What type of cancer is studied in the animation and where does it form? 2. How many cells are in the human body? 3. Identify two things that can cause mutation? 4. Why do normal cells usually reproduce? 5. What is angiogenesis? 6. What is metastasis?