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Aim: What are the major changes in the nucleus during cell division?

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Presentation on theme: "Aim: What are the major changes in the nucleus during cell division?"— Presentation transcript:

1 Aim: What are the major changes in the nucleus during cell division?

2 Mitosis 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.

3 Mitosis in multi-cellular organisms occurs for
Growth Repair Skin, epidermis and dermis Scar 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.

4 Asexual 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

5 Asexual Reproduction in Plants
Underground stems rhizomes bulbs corms and tubers

6 Asexual Reproduction in Plants
Bulbs and Tubers All of these types of asexual reproduction involve mitotic cell divisions.

7 Mitosis also occurs during early embryonic development
Fertilized egg Fetus The one-celled zygote must divide and become the millions of cells that make a human body or other multicellular organism

8 Cell division involves the process of Mitosis
Step 1 (S phase of Cell Cycle) Chromosomes Duplicate Chromosomes make more of themselves

9 Cell Division Step 3 Metaphase
Chromosomes line up in the middle of the cell What 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.

10 Cell Division Step 4 Anaphase
Double stranded chromosomes pull away from each other Chromosomes separate to the opposite poles of the cell. Plant Cell Animal Cell

11 Step 5 of Cell Division is Cytokinesis
Animal Cell Plant Cell How is it different? Animal cell membrane forms a cleavage furrow. Plant cell forms a cell plate that becomes a new cell wall.

12 Stages of tumor development
Cancer develops due to the loss of growth control in cells during cell division. D in situ cancer malignant B Hyperplasia A The stages of tumor development. A malignant tumor develops across time, as shown in this diagram. This tumor 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 num ber is probably less than ten. a. The tumor begins to develop when a cell experiences a mutation that makes the cell more likely to divide than it normally would. b. The altered cell and its descendants grow and divide too often, a condition called hyperplasia. At some point, one of these cells experiences another mutation that further increases its tendency to divide. c. This cell’s descendants divide excessively and look abnormal, a condition called dysplasia. As time passes, one of the cells experiences yet another mutation. d. This cell and its descendants are very abnormal in both growth and appearance. If the tumor that has formed from these cells is still contained within its tissue of origin, it is called in situ cancer. In situ cancer may remain contained indefinitely. e. If some cells experience additional mutations that allow the tumor to invade neighboring tissues and shed cells into the blood or lymph, the tumor is said to be malignant. The escaped cells may establish new tumors (metastases) at other locations in the body. C Dysplasia Stages of tumor development

13 Aim: What controls the cell cycle?
Readings on enzymes

14 Readings 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.

15 Ras Proteins Ras protein initiates the cell cycle by stimulating the cell cycle into the S phase and then it stops and waits for another signal to continue A mutation in the ras gene causes the cell to keep the cell cycle running with no checks and balances Proto-onco gene

16 P53 Tumor Supressor Binds to DNA and prevents replication
More than half of human cancers involve mutations in the P53 protein

17 Nibrin 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

18 MAD 1 The 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.

19 Some forms of chemotherapy prevent spindle formation.

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