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Chapter 13:The Cell Cycle

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1 Chapter 13:The Cell Cycle
Adapted from: Kim Foglia

2 How did you get from there to here?
And now look at you… How did you get from there to here?

3 Getting from there to here…
Cell division continuity of life = reproduction of cells reproduction unicellular organisms growth repair & renew Cell cycle life of a cell from origin to division into 2 new daughter cells Unicellular organisms Cell division = reproduction Reproduces entire organism& increase population Multicellular organisms Cell division provides for growth & development in a multicellular organism that begins as a fertilized egg Also use cell division to repair & renew cells that die from normal wear & tear or accidents

4 A bit about DNA DNA is organized in chromosomes
double helix DNA molecule associated proteins = histone proteins Nucleosome = a segment of DNA wrapped around 8 histone proteins DNA-protein complex = chromatin organized into long thin fiber


6 Chromosome Duplicated chromosome consists of 2 sister chromatids
meet at the centromere contain identical copies of the chromosome’s DNA Telomeres = repeated sequence at end of each arm p= short arm; q= long arm Centromeres are segments of DNA which have long series of tandem repeats = 100,000s of bases long. The sequence of the repeated bases is quite variable. It has proven difficult to sequence.


8 Prokaryotic Chromosome Structure
Bacteria have a one single loop of DNA

9 Types of Cells & Ploidy Levels
There are two types of human cells: somatic cells and gametes. Somatic Cells = body cells (brain, muscle, heart, liver, skin, etc) Contain 46 chromosomes in humans Diploid (2n)= cell that contains two sets of homologous chromosomes 23 PAIRS of homologous chromosomes = 46 TOTAL chromosomes Gametes = sex cells (sperm or egg) Contain 23 chromosomes in humans Haploid (n)= cell that contains one set of chromosomes

10 Fertilization When sperm meets egg a zygote is formed. A zygote is the first cell of the embryo. Which of the cells above are haploid (n)? Diploid (2n)?

11 Homologous Chromosomes
Chromosomes containing the same type of genetic information one comes from male parent, one comes from female parent DAD MOM

12 Homologous Chromosomes

13 The chromosomes diagrammed below are arranged in a karyotype, the 46 chromosomes have been arranged in homologous pairs.

14 The first 22 pairs of homologous chromosomes are called autosomes or autosomal chromosomes.
The 23rd pair of chromosomes determines the sex of the individual and are called sex chromosomes. The sex chromosomes of a female are XX. The sex chromosomes of a male are XY.

15 What’s the difference?

16 Cell cycle Cell has a “life cycle”
cell is formed from a mitotic division cell grows & matures to divide again cell grows & matures to never divide again G1, S, G2, M liver cells G0 epithelial cells, blood cells, stem cells brain nerve cells

17 Cell Division cycle Phases of a dividing cell’s life interphase
cell grows replicates chromosomes produces new organelles & biomolecules mitotic phase cell separates & divides chromosomes mitosis cell divides cytoplasm & organelles cytokinesis

18 Control of Cell Cycle

19 Interphase 90% of cell life cycle Characteristics
cell doing its “everyday job” produce RNA, synthesize proteins prepares for duplication if triggered Characteristics nucleus well-defined DNA loosely packed in long chromatin fibers

20 Interphase Divided into 3 phases: G1 = 1st Gap S = DNA Synthesis
G2 = 2nd Gap

21 Interphase G1 – First stage after division
Cell recovers from previous division Cell increases in size Doubles organelles Accumulates materials for DNA replication Cells do everyday jobs G0 – Some cells don’t complete the cycle (nerve and heart muscle) Continue normal cell operations No preparation for cell division Cells will operate in this stage until organism dies 9.1

22 Interphase S Stage – DNA synthesis occurs
At the beginning it contains chromosomes containing one DNA strand At the end each chromosome contains two identical strands of DNA Copies chromosomes G2 – Growth & final preparations for division Prepares for division Ends with mitosis Proteins that aid in mitosis are made in this stage Microtubules Nucleus well-defined DNA loosely packed 9.1

23 Interphase Nucleus well-defined Prepares for mitosis
chromosome duplication complete DNA loosely packed in long chromatin fibers Prepares for mitosis produces proteins & organelles

24 Mitosis copying cell’s DNA & dividing it between 2 daughter nuclei
Mitosis – division of the nucleus is divided into 5 phases Prophase Prometaphase metaphase anaphase telophase

25 Overview

26 Prophase Chromatin (DNA) condenses visible as chromosomes
chromatids fibers extend from the centromeres Centrioles move to opposite poles of cell Fibers (microtubules) cross cell to form mitotic spindle actin, myosin Nucleolus disappears Nuclear membrane breaks down

27 Prometaphase Proteins attach to centromeres
creating kinetochores Microtubules attach at kinetochores connect centromeres to centrioles Chromosomes begin moving

28 Kinetochore Each chromatid has own kinetochore proteins
microtubules attach to kinetochore proteins

29 Metaphase Spindle fibers align chromosomes along the middle of cell
meta = middle metaphase plate helps to ensure chromosomes separate properly so each new nucleus receives only 1 copy of each chromosome


31 Anaphase Sister chromatids separate at kinetochores
move to opposite poles pulled at centromeres pulled by motor proteins “walking”along microtubules increased production of ATP by mitochondria Poles move farther apart polar microtubules lengthen

32 Separation of chromatids
In anaphase, proteins holding together sister chromatids are inactivated separate to become individual chromosomes 1 chromosome 2 chromatids 2 chromosomes

33 Chromosome movement Kinetochores use motor proteins that “walk” chromosome along attached microtubule microtubule shortens by dismantling at kinetochore (chromosome) end Microtubules are NOT reeled in to centrioles like line on a fishing rod. The motor proteins walk along the microtubule like little hanging robots on a clothes line. In dividing animal cells, non-kinetochore microtubules are responsible for elongating the whole cell during anaphase, readying fro cytokinesis

34 Telophase Chromosomes arrive at opposite poles Spindle fibers disperse
daughter nuclei form nucleoli from chromosomes disperse no longer visible under light microscope Spindle fibers disperse Cytokinesis begins cell division

35 Cytokinesis Animals cleavage furrow forms
ring of actin microfilaments forms around equator of cell myosin proteins tightens to form a cleavage furrow, which splits the cell in two like tightening a draw string Division of cytoplasm happens quickly.

36 Cytokinesis in Animals
(play Cells Alive movie here)

37 Mitosis in whitefish blastula

38 Mitosis in animal cells

39 Cytokinesis in Plants Plants
vesicles move to equator line up & fuse to form 2 membranes = cell plate derived from Golgi new cell wall is laid down between membranes new cell wall fuses with existing cell wall

40 Cytokinesis in plant cell

41 Mitosis in plant cell

42 onion root tip

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