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Cell Reproduction. Starting at the beginning… Biologically speaking, where did YOU come from? Biologically speaking, where did YOU come from?

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Presentation on theme: "Cell Reproduction. Starting at the beginning… Biologically speaking, where did YOU come from? Biologically speaking, where did YOU come from?"— Presentation transcript:

1 Cell Reproduction

2 Starting at the beginning… Biologically speaking, where did YOU come from? Biologically speaking, where did YOU come from?

3 Cells How many cells make up a human body? How many cells make up a human body? Did you have the same number last year? What about when you were 2 years old? 2 months old? Did you have the same number last year? What about when you were 2 years old? 2 months old?

4 Cells Your body is made up of between 10 and 100 trillion cells. (100,000,000,000,000) Your body is made up of between 10 and 100 trillion cells. (100,000,000,000,000) One-thousandth of them die every day One-thousandth of them die every day

5 Cells Where do all these cells come from? Where do all these cells come from?

6 Cell Reproduction

7 Cell Specialization Different body cells perform different functions Different body cells perform different functions Examples: skin, nerve, red blood cells, liver cells, platelets Examples: skin, nerve, red blood cells, liver cells, platelets

8 Cell Specialization Different cells live for different amounts of time Different cells live for different amounts of time

9 Cellular Reproduction New cells are made from copies of old cells New cells are made from copies of old cells This process began occurring before you were born and will continue until after you die This process began occurring before you were born and will continue until after you die

10 Types of Cellular Reproduction MITOSIS – results in two identical cells; used for the majority of cells in the body MITOSIS – results in two identical cells; used for the majority of cells in the body MEIOSIS – results in four cells that are different from the “parents”; used for sex cells only MEIOSIS – results in four cells that are different from the “parents”; used for sex cells only

11 Mitosis Results in body growth or body repair Results in body growth or body repair Two new cells are called “daughter cells” Two new cells are called “daughter cells”

12 A Review of Cell Features Cell Membrane Cell Membrane Cytoplasm Cytoplasm Nucleus Nucleus Nuclear Membrane Nuclear Membrane Chromosomes – strands that carry a cell’s DNA Chromosomes – strands that carry a cell’s DNA Centrioles – strong, barrell-shaped organelle Centrioles – strong, barrell-shaped organelle

13 Mitosis Goals – duplicate chromosomes and move them to two new daughter cells Goals – duplicate chromosomes and move them to two new daughter cells

14 Before Mitosis Begins (interphase) Chromosomes are duplicated within the cells (exact copies) Chromosomes are duplicated within the cells (exact copies) Held together at center Held together at center Two strands are called “sister chromatids” Two strands are called “sister chromatids”

15 Mitosis Step 1: PROPHASE Step 1: PROPHASE –Sister chromatids thicken –Nuclear membrane breaks down –Two centrioles move apart –Fibers (strands of protein) form between centrioles

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17 Mitosis Step 2: METAPHASE Step 2: METAPHASE –Centrioles to opposite ends of cell –Fibers stretch between –Sister chromatids attach to fibers –Sister chromatids line up at center of the cell

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19 Mitosis Step 3: ANAPHASE Step 3: ANAPHASE –Sister chromatids pulled apart from partner –Fibers pull chromatids towards centrioles at opposite ends of the cell

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21 Mitosis STEP 4: TELOPHASE STEP 4: TELOPHASE –Each side now has complete set of chromosomes –Fibers disappear –Nuclear membrane re-forms –Cell membrane pinches inwards to form 2 cells

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23 Cytokinesis Division of the cytoplasm (cytokinesis) is complete. The two daughter cells are now separate cells in their own right. Cytokinesis

24 Mitosis in Plant Cells 2 Differences 2 Differences –No centrioles –Cell wall must re-form between new cells

25 INTERPHASE PROPHASE METAPHASE ANAPHASE TELOPHASE

26 How to remember order of phases? In Patiki, Men Are Tough. Stages of mitosis/meiosis including interphase as a phase! Interphase, Prophase, Metaphase, Anaphase, Telophase. In Patiki, Men Are Tough. Stages of mitosis/meiosis including interphase as a phase! Interphase, Prophase, Metaphase, Anaphase, Telophase.

27 Importance of Chromosomes All chromosomes come in pairs All chromosomes come in pairs Humans have 23 pairs, so a normal cell has 46 chromosomes Humans have 23 pairs, so a normal cell has 46 chromosomes All cells need a full set to function properly (except sex cells) All cells need a full set to function properly (except sex cells)

28 Chromosome Number Before mitosis begins, cells have two of each chromosome (2N) Before mitosis begins, cells have two of each chromosome (2N) After chromosomes duplicate, cells have four of each chromosome (4N) After chromosomes duplicate, cells have four of each chromosome (4N) After mitosis, cells have two of each chromosome (2N) After mitosis, cells have two of each chromosome (2N)

29 Meiosis

30 Meiosis Process that creates gametes (eggs and sperm) Process that creates gametes (eggs and sperm) Cells divide twice Cells divide twice

31 Chromosome Number Cells start with two of each chromosome (2N) Cells start with two of each chromosome (2N) Chromosomes double (4N) Chromosomes double (4N) Pairs divide (2N) Pairs divide (2N) Sister chromatids divide (N) Sister chromatids divide (N)

32 Importance of Meiosis During fertilization, sperm (N) and egg (N) fuse to create one cell (2N) During fertilization, sperm (N) and egg (N) fuse to create one cell (2N) New cell has complete set of chromosomes (half from mother, half from father) New cell has complete set of chromosomes (half from mother, half from father)

33 Chromosome Number N represents number of PAIRS of chromosomes N represents number of PAIRS of chromosomes 2N = total number of chromosomes in a normal cell 2N = total number of chromosomes in a normal cell N – total number of chromosomes in a gamete (sex cell) N – total number of chromosomes in a gamete (sex cell)

34 Steps of Meiosis Step 1 Step 1 –PROPHASE I –Sister chromatids thicken –Nuclear membrane breaks down –Two centrioles move apart –Fibers (strands of protein) form between centrioles

35 Steps of Meiosis Step 2: Step 2: –METAPHASE I –Centrioles to opposite ends of cell –Fibers stretch between –Sister chromatids attach to fibers –Sister chromatids line up at center of the cell

36 Steps of Meiosis Step 3: Step 3: –ANAPHASE I  Sister chromatids DO NOT separate. –TELEPHASE I

37 Steps of Meiosis Step 4: Step 4: –PROPHASE II –Cell has been split in two –No nuclear membrane forms

38 Steps of Meiosis Step 5: Step 5: –Occurs in both cells –METAPHASE II

39 Steps of Meiosis Step 6: Step 6: –ANAPHASE II –TELEPHASE II

40 THE MOST IMPORTANT DIFFERENCE In the first cell division, CHROMOSOME PAIRS are pulled apart. In the first cell division, CHROMOSOME PAIRS are pulled apart. In the second cell division, SISTER CHROMATIDS are pulled apart. In the second cell division, SISTER CHROMATIDS are pulled apart.

41 Meiosis Meiosis: the division of a diploid nucleus to form four haploid genetically different daughter nuclei. Meiosis: the division of a diploid nucleus to form four haploid genetically different daughter nuclei. Role of Meiosis Role of Meiosis Increases genetic variation in the population – role in evolution Increases genetic variation in the population – role in evolution Makes sexual reproduction possible Makes sexual reproduction possible Gamete formation in animals, fungi, protoctista e.g. Man Gamete formation in animals, fungi, protoctista e.g. Man Site of Meiosis Site of Meiosis Animals Animals testis - forming sperm, the haploid male gametes; testis - forming sperm, the haploid male gametes; ovary - forming egg cells, the haploid female gametes. ovary - forming egg cells, the haploid female gametes. Flowering plants: Flowering plants: anther of the stamen - forming the haploid male spores (microspores), anther of the stamen - forming the haploid male spores (microspores), ovule of ovary - forming the haploid female spores (megaspores). ovule of ovary - forming the haploid female spores (megaspores).

42 Cancer and Aging

43 Cancer/Aging How are cancer and aging similar? How are cancer and aging similar?

44 Cancer/Aging Changes in rates of mitosis Changes in rates of mitosis

45 Aging What properties of a person’s body change as they age? What properties of a person’s body change as they age? Physically? Physiologically? Physically? Physiologically?

46 Cancer Rapid, abnormal, uncontrolled mitosis Rapid, abnormal, uncontrolled mitosis What causes cancer? What causes cancer?

47 Cancer Causes Viruses Viruses Chemicals Chemicals Radiation Radiation


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