Presentation on theme: "Aim: What are the major changes in the nucleus during cell division?"— Presentation transcript:
1Aim: What are the major changes in the nucleus during cell division?
2Mitosis in a single celled organism This type of reproduction involves no exchange of genetic material, and is a type of asexual reproduction. This form of asexual reproduction is often called 'fission'Paramecium, like other ciliates, usually reproduces by splitting in two, forming two virtually identical individuals from one organism. There is one parent.
3Mitosis in multi-cellular organisms occurs for GrowthRepairSkin, epidermis and dermisScar formation is a natural process that results from replacement tissue being somewhat structurally and functionally different than the original tissue that was injured.A scar is the marking that remains after tissue damaged from a cut, burn, or other wound has healed. The most familiar scars appear on the surface of the skin, though they also can develop on tissues located inside the body.
4Asexual Reproduction Budding Although capable of sexual reproduction, hydras reproduce most of the year by producing external asexual buds that eventually pinch off at the base and become new individuals. Budding Hydra
5Asexual Reproduction in Plants Underground stemsrhizomesbulbscorms andtubers
6Asexual Reproduction in Plants Bulbs and TubersAll of these types of asexual reproduction involve mitotic cell divisions.
7Mitosis also occurs during early embryonic development Fertilized eggFetusThe one-celled zygote must divide and become the millions of cells that make a human body or other multicellular organism
8Cell division involves the process of Mitosis Step 1(S phase of Cell Cycle)Chromosomes DuplicateChromosomes make more of themselves
9Cell Division Step 3 Metaphase Chromosomes line up in the middle of the cellWhat kind of cells are these?Pink stain pictures are animal cells.Brown stained pictures are plant cells.How is cell division different in each type of cell?Animal cell – centrioles produce the spindle fibers that will pull the chomosomes apart.The cell pinches in with the cell membrane producing what is called animal furrows.The plant cell produces a cell plate that becomes the cell wall made of cellulose.
10Cell Division Step 4 Anaphase Double stranded chromosomes pull away from each otherChromosomes separate to the opposite poles of the cell.Plant CellAnimal Cell
11Step 5 of Cell Division is Cytokinesis Animal CellPlant CellHow is it different?Animal cell membrane forms a cleavage furrow.Plant cell forms a cell plate that becomes a new cell wall.
12Stages of tumor development Cancer develops due to the loss of growth control in cells during cell division.D in situ cancermalignantB HyperplasiaAThe stages of tumor development. A malignant tumor develops across time, as shown in this diagram. Thistumor develops as a result of four mutations, but the number of mutations involved in other types of tumors can vary.We do not know the exact number of mutations required for a normal cell to become a fully malignant cell, but the number is probably less than ten. a. The tumor begins to develop when a cell experiences a mutation that makes the cell morelikely to divide than it normally would. b. The altered cell and its descendants grow and divide too often, a conditioncalled hyperplasia. At some point, one of these cells experiences another mutation that further increases its tendency todivide. c. This cell’s descendants divide excessively and look abnormal, a condition called dysplasia. As time passes, oneof the cells experiences yet another mutation. d. This cell and its descendants are very abnormal in both growth andappearance. If the tumor that has formed from these cells is still contained within its tissue of origin, it is called in situcancer. In situ cancer may remain contained indefinitely. e. If some cells experience additional mutations that allow thetumor to invade neighboring tissues and shed cells into the blood or lymph, the tumor is said to be malignant. Theescaped cells may establish new tumors (metastases) at other locations in the body.CDysplasiaStages of tumor development
13Aim: What controls the cell cycle? Readings on enzymes
14Readings on Enzymes You will read one article from the folder What is its function?How can cancer develop when this regulation is disrupted?Share what you read with your group.
15Ras ProteinsRas protein initiates the cell cycle by stimulating the cell cycle into the S phase and then it stops and waits for another signal to continueA mutation in the ras gene causes the cell to keep the cell cycle running with no checks and balancesProto-onco gene
16P53 Tumor Supressor Binds to DNA and prevents replication More than half of human cancers involve mutations in the P53 protein
17Nibrin and ATM Repairs chromosomal damages before Mitosis takes place A mutation in this protein allows the cell to move onto mitosis with the damaged chromosomes
18MAD 1The spindle checkpoint prevents anaphase from occurring until chromosomes have attached to the spindle fibers.Mutation of this protein causes abnormal chromosome numbers in cancer cells.
19Some forms of chemotherapy prevent spindle formation.