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Cell Division.

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Presentation on theme: "Cell Division."— Presentation transcript:

1 Cell Division

2 4 day old mouse cells

3 Section 1 Vocabulary 1. Cell cycle 2. Interphase 3. Mitosis
4. Cytokinesis 5. Chromosome 6. Chromatin

4 Cells are small! But why? As cells get bigger, the surface area to volume ratio changes and makes it harder for certain things to occur in the cell!

5 -causes problems with the transport of materials             -larger cells need more "stuff" but only so much can cross the cell membrane at a time   

6 Surface area to volume lab demo
Why are cells so small???

7 Lab groups of 6 2 will measure/time the 1cm cube
On your own notebook paper Write: Title, data chart, calculations for your cube, observations as it happens. Add the group data to your data chart. Put your paper in your notebook. The group will compile one report from this to turn in together for a grade! Answer all questions

8 Cell communication Cell communication can not take place if the cell is too large because it involves signaling proteins that would be too far away from the molecules.

9 -cell division solves a cell's size problem
a cell needs a large surface area relative to its volume           (a high surface-to-volume ratio) to survive When the cell reaches its size limit it will stop growing or it will divide!

10 Why do we need cell division?
to grow, replace worn-out or damaged cells, or reproduce asexually.

11 Cell cycle

12 Stages of Interphase Normal cell day to day life of a cell!!
-interphase = when the cell grows, carries out cellular functions and replicates its DNA to prepare for the division phase! Or the period between cell divisions. It is the longest of the phases! -Gap 1 (G1)      -cell growth & development -DNA Synthesis (S)      -replication of DNA -Gap 2 (G2)      -creation of materials needed for division Doubling the nuclear material in the S-phase provides enough DNA to generate 2 complete nuclei at the end of mitosis.  This ensures that each daughter cell has the same number of chromosomes as the original parent cell. 

13 Mitosis and Cell Division
All cells go through a cell cycle composed of cell division portion (mitosis) and "resting period" (interphase).

14 How do some cells know to become lung cells and others to become heart or muscle?

15 Genes on the chromosomes (made up of DNA) contain the instructions for building the proteins required for each cell type. Cell to cell communication helps cells differentiate into the specialized cells.

16 Nucleus Usually large enough to be seen with light microscope. Double membrane (nuclear envelope) bound organelle with pores. The nucleus is the "control center" for the cell since it contains the hereditary material

17 DNA within chromatin. Condensed chromatin (during cell division) is visible with the microscope as chromosomes. Inside the nucleus is a dark staining region called the nucleolus which is involved in making ribosomal RNA (rRNA). Think of this as city hall (archives genealogical data)!

18 How does a Eukaryotic cell reproduce?
DNA is organized into chromosomes and segments called genes that code for proteins.


20 How DNA is packaged! 6 feet in a cell, WOW!

21 Chromosomes are DNA and protein that become visible when the cell is ready to divide.

22 Making a chromosome 1. DNA is 1st copied 2 identical strands make up chromatids 2nd the DNA wraps around proteins called histones the chromatids connect at the center called the centromere.

23 How chromosome # and structure affect development
Each body cell (somatic cell ) has 23 different chromosome pairs for a total of 46 Each chromosome has thousands of genes on them that are essential to life!

24 What are sets of chromosomes called?
Homologous pairs Homologous chromosomes are ones that are similar in size, shape and information that they contain. One comes from each parent


26 2 sets of 23 make up the 46 in a human.
1 set from mother 23 1 set from father 23 46


28 Chromosomes Are present in the nucleus. Occur as chromatin (uncondensed) and chromosomes (condensed during cell division). Composed of a strand of DNA and associated proteins. The DNA stores and transmits genetic information, while the proteins are important for packaging these long strands of DNA.


30 Details of DNA structure
DNA is a double helix composed of a backbone of phosphate and sugar groups. From the sugars, nucleotide bases protrude. Four nucleotides exist in DNA: A, C, G, and T. A pairs with T, G with C. The two strands run antiparallel (opposite directions) and the bases hydrogen bond together. Genes are composed of sections of DNA that encompass hundreds to thousands of base pairs.


32 Prokaryotic Cells Since Prokaryotic cells do not have a nucleus they reproduce my a much simpler method with out the cell cycle that eukaryotes have. It is called binary fission.

33 Binary Fission The chromosome replicates and the cell divides making 2 exact copies of the cell.

34 Asexual reproduction

35 There is little room for variation in this process so the cells are almost like clones of each other!

36 1. What factor limits the size of a cell the most
1. What factor limits the size of a cell the most? Surface area to volume ratio_ 2. How do most substances move from one area of the cell to another? Difusion 3. Is this movement easier when the cell is small or large? Small 4. How does cell size affect cell communication? If it gets too large it will no be able to communicate.

37 5. Draw the cell cycle label the parts of the phases
5. Draw the cell cycle label the parts of the phases. Include G1, S, G2 Mitosis, and Cytokinesis.

38 6. Which phase seems to be the longest. interphase 7
6. Which phase seems to be the longest? interphase What happens in Mitosis? The genetic material divides 8. What happens in cytokinesis? The cytoplasm and organelles divide 9. What happens in the G1 phase of interphase? -cell growth & development 10. What happens in the S phase? -replication of DNA 11. What happens in the G2 Phase? creation of materials needed for division 12. What is the difference between chromosomes and chromatin? Chromosomes are packaged and only show up when the cell is ready to divide, chromatin is the unwound form of DNA when it is in use by the cell. 13. Do prokaryotic cells divide with this cell cycle? No What is the method they use called? Binary fission

39 How does a Eukaryotic cell reproduce?
DNA is organized into chromosomes and segments called genes that code for proteins.

40 Section 2 Vocabulary: 1. Prophase 2. Metaphase 3. Anaphase
4. Telophase 5. Sister chromatid 6. Centromere 7. Spindle apparatus

41 Stages of mitosis The division of the nucleus is considered a separate process from the division of the cytoplasm. Mitosis: nucleus division Cytokinesis: cytoplasm division


43 chromosome Spindle apparatus

44 spindle




48 Mitosis video!

49 Prophase the chromatids continue to condense; the nuclear envelope and nucleolus disintegrate; the spindle apparatus forms (fibers composed of microtubules responsible for the movement of the chromosomes); kinetochores form (protein containing structures that serve to attach the chromatids to the spindle fibers)

50 Metaphase spindle fibers attach to chromosomes at the kinetochores;
kinetochore fibers orient the chromosomes so that only one chromatid will move to each pole {8-13R} the central region where the chromosomes align is called the equator or metaphase plate

51 Anaphase shortest phase;
sister chromatids are separated at the centromeres and are pulled to opposite poles

52 Telophase Telophase: chromosomes uncoil, spindle disappears,
nuclear envelope reforms, nucleoli form; cytokinesis takes place here by the formation of a cell plate

53 Interphase: period between cell divisions which consists of processes associated with cell growth (expansion) and preparation for mitosis

54 Result of mitosis Where there was once one cell, there are now two "daughter cells". Each cell is identical genetically since the genetic material was simply duplicated during interphase. This is essentially the same as cloning. The chromosome number remains the same.

55 Animations Biology Learning Center Molecular Expressions Mitosis World
Onion root tips on line

56 Interphase Normal, non dividing cell

57 Make a cell divide!! 1. Tie a piece of string into a big circle to represent the cell membrane. 2. Cut a piece of string to represent the nuclear membrane; do not tie this one into a circle. 3. Cut 6 chromosomes out of string, make sure they each have a “copy” of them selves.

58 Play with your chromosomes!!!
First make a cell with 6 chromosomes in interphase

59 The chromosomes replicate
Match them with their copy! Just twist the two strings together to represent the centromere The black star represents the centromere that connects the two sister chromatids

60 Make the cell go through all of the phases

61 Prophase: 1. nuclear membrane dissolves 2. Identical chromosome pairs are attached, into "sisters chromatids", which are attached to each other by a centromere 3. In animal cells, centrioles migrate to opposite ends of cell (poles) 4. Spindle fibers form between poles to attach to chromatids

62 Metaphase: Sister chromatids line up at the equator of cell

63 Anaphase: 1. Chromatid pairs are separated and each is pulled to an opposite pole 2. Two identical groups of chromosomes are now clustered at opposite sides of cell

64 Telophase: 1. "parent" cell begins to separate into two "daughter" cells, each having an identical set of chromosomes

65 Telophase: While the genetic components are dividing up, CYTOKINESIS is also occurring (division of cytoplasm) 2. Nuclear membranes re-form 3. Spindle fibers break down 4. Cells return to interphase

66 2 Daughter cells in interphase
And the process starts again…

67 The major differences in how plant and animal cells divide are:
Animal cells have centrioles to mark the poles, plant does not Animal cells divide differently than plant during cytokinesis In plant cells, a cell plate forms in the middle of the dividing cell and expands outward until a complete wall is formed between the two daughter cells In animal cells, a cleavage furrow forms at the outer edges and constricts inward until the two daughter cells are separated

68 Animal cells

69 Plant cell


71 The Importance of Mitosis
Mitosis ensures that each new body cell has the same genetic makeup as its parent. Mutations can and do occur occasionally but, for the most part, all of your body cells have identical DNA Mitosis not only functions to replace cells and make new cells (growth) it also reduces cell size. Can you think of three reasons that cell size must remain so small?

72 Skin replacement

73 Wound healing




77 Onion root tip

78 Onion root tips on line

79 Online Onion Root Tips

80 Plant mitosis

81 1. What divides in mitosis? The DNA
2. Draw the phases of mitosis and briefly describe what happens in each phase.

82 3. Why do cells need to undergo mitosis
3. Why do cells need to undergo mitosis? To reproduce, to replace themselves when they get old or damaged to maintain the chromosome number. 4. What are 3 differences in animal and plant cell mitosis? Animal cells have centrioles, a cleavage furrow during cytokinesis and no cell plate. The plant cell forms a cell plate to produce a new cell wall between the new cells. 5. What happens in cytokinesis? The cytoplasm and organelles are divided between the two new cells.

83 SC.912.L.16.15 Compare and contrast binary fission and mitotic cell division.
1. Prokaryotes reproduce by binary fission. How is binary fission different from mitotic cell division? In prokaryotes there is no nucleus and a single chromosome so there are not phases , the cell simply replicates the DNA and then divides in two making exact copies of it self.

84 reflections Do your reflection for section 2 benchmarks

85 Section 3 vocabulary: 1. Cyclin, 2. Cancer, 3. Carcinogen,
4. Apoptosis, 5. Stem cell

86 Cell cycle regulation The rate of the cell cycle is important.
Rate varies depending on the cell type. Cyclins, proteins, bind to enzymes to start the parts of the cell cycles. G1 has a cyclin /CDK complex to to get it started… so do several other places in the cell cycle.

87 The cell cycle in eukaryotes is controlled by many proteins
The cell cycle in eukaryotes is controlled by many proteins. Control occurs at three principal checkpoints

88 1. Cell growth (G1) checkpoint
2. DNA synthesis (G2) checkpoint. 3. Mitosis checkpoint

89 When Control Is Lost: Cancer
Cancer is essentially a disorder of cell division. Cancer cells do not respond normally to the body’s control mechanisms.

90 Cancer cells


92 There are check points along the way to make sure the processes are working properly.
If the checkpoints are not working properly uncontrolled growth can occur. This is how cancer can occur. Mutations in cell proteins that check the cycle can cause cancer. Carcinogens, substances that cause cancer, can cause damage to the DNA to make faulty proteins.

93 apoptosis Programmed cell death. The cell shrinks and dies.
Examples include the cells in-between the fingers and toes die at the correct time to prevent webbing. Some damaged cells die to prevent damage to the entire organism.

94 Stem cells Unspecialized cells that can develop into specialized cells under the correct conditions. 2 types Embryonic Adult stem cells

95 SC.912.L Explain the relationship between mutation, cell cycle, and uncontrolled cell growth potentially resulting in cancer. 1. What controls the rate at which the cell divides? The types of cell, the regulating proteins of the cell cycle. 2. What happens when the control system no longer works? Uncontrolled growth or cancer can result. 3. What is cancer? Uncontrolled cell growth. 4. What types of things can cause cancer? DNA mutations , chemicals, environmental causes, genetic mistakes 5. Does the body have ways to try to prevent cancer from harming it? Yes there are check points and ways to destroy cells with defects.

96 Section 3 reflections are due:
Monday! Include 1. the benchmark 2. Your level of understanding, any questions you still have about this material 3. The answer to this benchmark, even if you have to look it up in your notes or the book! Chapter 10 section 1 vocabulary due Monday s well…. See the board for the list

97 There is little room for variation in this process so the cells are almost like clones of each other!

98 Asexual reproduction

99 Comparing Mitosis and Meiosis
Observational activity In your groups, use the pictures in the book ( pages 249 and 273) to draw the basic diagrams of the phases of mitosis and meiosis side by side on the poster paper. Make a chart/vendiagram of what they have in common and what differences they have. Be prepared to share your results with the class!

100 Review How prokaryotic and eukaryotic division differs What is a gene
What limits the size of a cellthe most? What are chromatids? How do chromosomes exist in your body?

101 How is DNA packaged? Which phase is the longest? What is the order of the cell cycle? Know what happens in each phase Know the phases of mitosis

102 How can mutations alter the cell cycle?
Why do organisms need to use mitosis? What is DNA composed of? What is the shape of DNA? What is binary fision? What is apoptosis?

103 What causes cancer? What is chromatin? What is the DNA doing when it is in the chromatin form? What are stem cells?

104 chromosomes

105 Duplicated and unduplicated

106 Homologous chromosomes

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