Today you need: notebook, pen or pencil, textbook, colors to share, colored paper foldable. later

Transcription

1 CELL DIVISION

2 Objectives Students will learn what causes a cell to divide and how it happens. They will explore all parts of the cell cycle and mitosis. They will discuss what happens when this process malfunctions causing mutations or cancer

3 Today you need: notebook, pen or pencil, textbook, colors to share, colored paper foldable Bellwork: later Carefully copy, label and color the cell cycle diagram on page 130

4 Cell Growth Does an animal get larger because each cell increases in size or because it produces more of them?

5 Cell Growth As you might have guessed, living things grow by producing more cells. The koalas have the same size cells, just one has more then the other.

6 Limits to Cell growth The larger a cell becomes, the more demands the cell places on its DNA. In addition, the cell has more trouble moving enough nutrients and wastes across the cell membrane. The cell can t grow. It must reproduce!

7 Ratio of surface area to volume:

8 Cell Division The process by which a cell divides into two new daughter cells is called cell division. Before cell division occurs, the cell replicates, or copies, all of its DNA. This replication solves the info. problem.

9 Cell Division What do you think would happen if a cell were simply to split into two without any advance preparation?

10 Chromosomes In eukaryotic cells, the genetic information that is passed on from one generation of cells to the next is carried by chromosomes. The cells of every organism have a specific number of chromosomes. Each chromosome consists of two identical sister chromatids. When the cell divides, the sister chromatids separate and go to each of the new cells.

11 Chromosome Each pair of chromatids is attached at an area called a centromere. Centromeres are usually located near the middle of the chromatids, although sometimes can be found at each end.

12 The Cell Cycle The cell cycle is the series of events that cells go through as they grow and divide. During the cell cycle: - A cell grows - Prepares for division - And divides to form to daughter cells

13 Events of the Cell Cycle There are four phases of the Cell Cycle. G1 phase period where cell does most of their growing S phase chromosomes are copied and the synthesis of DNA molecules takes place. (DNA Replication) G2 phase usually the shortest of the phases. The phase where essential organelles are constructed. More growth and M phase Cell Division.Mitosis

14 I P on a MAT *preparation between split Interphase *mitosis Prophase Metaphase Anaphase Telophase *cells split Cytokenesis Steps of Cell Division

15 Interphase Stage between cellular division. Also known as the G1, S, and G2 stages of the cell cycle. In Interphase the cell is allowed to grow, copy its DNA and check for crucial genetic mistakes.

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17 Mitosis Mitosis (M phase) steps which include the process for asexual cell division. Biologists divide the events of mitosis into four phases: - Prophase - Metaphase - Anaphase - Telophase Depending on the type of cell, the four phases may last anywhere from a few minutes to several days.

18 Mitosis Let s look at each of the parts of mitosis.. and practice our hand symbols as we go.

19 Prophase - The first and the longest phase of mitosis, prophase can take as much as 50 to 60 percent of the total time required to complete mitosis. - During prophase in animal cells, the centrioles separate and take up positions on opposite sides of the nucleus. - The centrioles help organize the spindle, fanlike microtubule structure that helps separate the chromosomes.

20 Prophase chromosomes appear-chromatin condenses to form chromosomes the nucleolus disappears the cell membrane begins to break down

21 Metaphase chromosomes align along the equator of the cell pulled by the spindle fibers Spindle fiber that are attached to the poles connect to the centromeres Short Phase

22 Early Anaphase chromosomes are pulled to the poles by the contraction of the spindle fibers chromatids are separated at the centromere

23 Late Anaphase chromosomes begin to move to the opposite poles Karyokinesis the energy for this process is provided by the mitochondria

24 Early Telophase the new cell wall begins to form to separate the new cell the chromosomes begin to form a nucleus

25 Late Telophase the chromosomes start to uncoil and become less dense Nuclear membrane reassembles Nucelolus reappears Plasma membrane begins to separate Cell plate forms two new identical cells are formed

26 Cytokinesis Cytokinesis is the division of the cytoplasm of a parent cell. Microfilaments form a ring around the equator. When the microfilaments contract-pinches makes a furrow

27 Cytokinesis You may either consider it the end of Mitosis or the beginning of Interphase. While each daughter cells gets identical sets of DNA, the cytoplasm and organelles are only roughly divided equally between the two cells. Parent chromosome #= Daughter chromosome#

28 all four stages of mitosis can be seen in this picture. note the process by which the red and blue chromosome s separate. Mitosis

29 MITOSIS

30 What time is it Mrs. Weatherall???? It s foldable time!!!!!!!!!

31 :// VlN7K1-9QB0

32 Regulating the Cell Cycle If we grow by cell division, then why do we stop growing? Multi-cellular organisms cell growth is controlled. For example, in the human body, most muscle and nerve cells don t divide at all once they have developed, whereas skin cells and blood cells divide rapidly.

33 What time is it Mrs. Weatherall???? It s foldable time!!!!!!!!!

34 Today you need: textbook, notebook, pen or pencil, worksheet, question packet Bell work: copy & answer 1. What happens during cytokinesis?(136) 2. Why do we need to make new cells? (4 reasons)

35 Today you need: worksheet, pen or pencil, 4 hi-liters to share, Bell work: copy and answer: 1. If an animal has 60 chromosomes, how many cells does it produce in one cell cycle? 2. How many chromosomes would be in each cell? 3. If those cells were for that animal s sperm or egg how many chromosomes would they have and why?

36 Controls on Cell Division What would happen if the cells continued to divide? When cells come into contact with other cells, they respond by not growing. How does this relate to how your body responds to a cut or a bone fracture?

37 Cell Cycle Regulators Scientists discovered that cells in mitosis contain a protein called cyclin when injected in a non-dividing cell, would cause a miotic spindle to form. Cyclins regulate the timing of the cell cycle in eukaryotic cells.

38 Other Cell Cycle Regulators Internal regulators- proteins that respond to events inside the cell. For example: several regulatory proteins make sure that a cell does not enter mitosis until all its chromosomes have been replicated. - External regulators- proteins that respond to events outside the cell. For example: external regulators direct cells to either speed up or slow down the cell cycle.

39 Uncontrolled Cell Growth Why is cell growth regulated so carefully? Cancer- a disorder in which some of the body s own cells lose the ability to control division. Cancer cells do not respond to the signals that regulate the division of most cells.

40 Skin Cells

41 Practice Hand Signs IPMAT

42 worksheet Let s do the mitosis worksheet together

43 EOC questions Put away everything except your notebook. Everyone will need a dry erase board, marker and some paper towel.