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Mitosis & Cytokinesis. Why do Eukaryotic cells divide by Mitosis? Growth & Repair for multicelled organisms Reproduction of single celled organisms Amobea.

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Presentation on theme: "Mitosis & Cytokinesis. Why do Eukaryotic cells divide by Mitosis? Growth & Repair for multicelled organisms Reproduction of single celled organisms Amobea."— Presentation transcript:

1 Mitosis & Cytokinesis

2 Why do Eukaryotic cells divide by Mitosis? Growth & Repair for multicelled organisms Reproduction of single celled organisms Amobea Reproducing

3 Cells dividing by Mitosis……. Identical to original cell Same chromosome # Identical chromosome makeup Skin

4 What are chromosomes? A chromosome is an organized structure of DNA and protein that is found in cells. It is a single piece of coiled DNA containing many genes, regulatory elements and other nucleotide sequences.

5

6 Sister Chromatids

7 So where is DNA located ? In the Nucleus In the Chromosomes

8 Cell division requires coordinated division of chromosomes (mitosis) ….. …… and division of the cytoplasm (cytokinesis).

9 From Birth to Rebirth, a Cell Progresses Through Characteristic Stages That Constitute the Cell Cycle. In multicellular organisms like us, progress through the cell cycle is carefully regulated.

10 Stages of Mitotic Cell Division Interphase - intermission Prophase - 1st Metaphase - middle Anaphase - apart Telophase – far or seperate

11 Interphase “Intermission” Normal metabolic activities Major state DNA = chromatin

12 Late Interphase Prepares for mitosis DNA doubles = Sister chromatids Centrioles double in animals

13 Prophase Nuclear membrane disappears Doubled DNA = condensed “chromosomes” visible Spindle fibers

14 Metaphase Chromosomes line up mid- cell Facing inward

15 Anaphase Chromosomes move to opposite poles at Centrioles in animals Spindle apparatus in plants

16 Telophase Cells divide Cell plate or membranes form Nucleus reappears

17 Cytokinesis : cell’s cytoplasm divides & splits apart

18 Plant versus Animal Mitosis Plant: Cell wall from cell plate in telophase Spindles Animal: No cell wall membrane during cytokinesis Centrioles

19 In Animal Cells, a Cleavage Furrow Forms and Separates Daughter Cells Cleave furrow in a dividing frog cell.

20 Animal Telophase Interphase

21 The Plant Cell Wall Forces Cytokinesis to Play by Different Rules

22 Plant Anaphase Interphase

23 Spindle & spindle fibers: Pull apart the sister chromatids Spindle fibers

24 Returns to Interphase “Intermission” Normal metabolic activities Major state DNA = chromatin

25 DNA and Its Faithful Replication – The Knit of Identity Because DNA stores genetic information and is faithfully replicated, information is passed largely unaltered from cell-to-cell, generation-to- generation.

26 Proteins and Their Production – The Primary Reason for DNA

27 Cell Division Demands Coordination of DNA Replication, Mitosis and Cytokinesis

28 DNA Replication – Simple in Principle, Complicated in Practice

29 DNA is Packaged into Chromosomes DNA in the cell is virtually always associated with proteins. The packaging is impressive – 2 meters of human DNA fit into a sphere about meters in diameter. chromatin duplicated chromosome

30 The Link Between DNA Replication and Chromosome Duplication

31 DNA is Condensed into Visible Chromosomes Only For Brief Periods in the Life of a Cell 95% of the time, chromosomes are like this. (chromatin) Easily visible chromosomes are apparent perhaps 5% of the time in an actively growing cell and less in a non-growing cell.

32 A Karyotype is an Arranged Picture of Chromosomes At Their Most Condensed State A normal human karyotype Boy or girl? Note that almost all chromosomes come in homologous pairs.

33 From Birth to Rebirth, a Cell Progresses Through Characteristic Stages That Constitute the Cell Cycle In multicellular organisms like us, progress through the cell cycle is carefully regulated.

34 The Knit of Identity - Mitosis Precisely and Evenly Divides Duplicated Chromosomes Precisely dividing the duplicated chromosomes has the consequence of providing each new cell with an identical and complete set of genetic instructions. interphase prophase metaphase

35 Mitosis Precisely and Evenly Divides Duplicated Chromosomes Cytokinesis is the process of cell division and it is distinct and separable from mitosis.

36 Mitosis in Action Blue shows DNA, green shows spindle fibers.

37 Cancerous cells ……... 1.Divide too many times 2.Divide into more than two cells! Masses of cells = “tumors” benign malignant

38 Cancer Is One Outcome of A Runaway Cell Cycle Licentious division - prostate cancer cells during division.


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