The cytoskeletal system, cell cycle and DNA replication                         Hilary Mok                       Yolande L...
The Cytoskeletal System• An intricate network of protein filaments that  extend throughout the cytoplasm• Highly dynamic->...
Functions of the cytoskeleton• Establishes cell shape• Provides mechanical  strength• Locomotion• Chromosome separation  i...
Components of cytoskeletal system1. Intermediate Filaments2. Microtubules3. Actin Filaments• Each type of filament has dis...
Intermediate filaments (IF)• 8-10nm• Strong and Rope-like• Form a network throughout the cytoplasm of  most animal cells• ...
Functions & Properties of IF• Have great tensile strength for structural  support• Strengthens cells against mechanical st...
Categories of IF                                      Intermediate Filaments                      Cytoplasmic             ...
Cytoplasmic IF• Keratin   – Span interiors of epithelial cell from one   side to the other   – Forms a cable of high tensi...
Nuclear IF• Nuclear lamina  – Just beneath nuclear membrane  – Underlies and strengthens the nuclear envelope in    all eu...
Hutchinson-Gilford Progeria Syndrome               (HGPS)               • Caused by mutation of gene                 that ...
• Affects children of all ethnicity• Cause individuals to appear to  age prematurely• Signs: growth failure, loss of  body...
Ashley Hegi, 16
Microtubules• Long, hollow cylinder , made from the protein  tubulin• 25nm in diameter• More rigid than actin filaments• N...
Axonemal microtubules• Highly organised, stable microtubules in  specific subcellular structure associated with  cellular ...
Cytoplasmic microtubules• Loosely organised, dynamic  network of microtubules• Variety of functions: formed  mitotic and m...
Actin Filaments (Microfilaments)• 2-stranded helical polymers of the protein actin• Thin and flexible structure, diameter ...
2 main functions of Actin filaments• Muscle contraction
2. Cell locomotion   (“crawling”)E.g. amoebae
Cell Cycle• Duplication and division• Essential mechanism by which all living things  reproduce• Details vary from one org...
Cell cycle control system• Ensures that events of the cell cycle (DNA  replication, mitosis, etc) occur in a set  sequence...
M phase (Mitosis)• A process of nuclear division• Replicated copies of a cell’s DNA are organised into  chromosomes• Ident...
Prophase• Replicated chromosomes consisting of 2  closely associated sister chromatids condense• Nuclear envelope breaks d...
Prometaphase• Starts abruptly with the breakdown of the nuclear  envelope• Chromosomes attach to spindle microtubules via ...
Metaphase• Kinetochores of the chromosomes line up along  the equator of the cell, moved by the spindle  microtubules• The...
Anaphase• Begins when the sister chromatids synchronously  separate• Centromere holding sister chromatids together  divide...
Telophase• 2 groups of chromosomes reach the opposite poles of  the spindle• As a new nuclear envelope starts to form arou...
C phase (cytokinesis)• Division of cytoplasm and organelles• Cytoplasm is divided into 2 by a contractile ring of  actin a...
Meiosis I (reduction division)
Meiosis II (separation division)
Difference between Mitosis and MeiosisMitosis                          MeiosisOccurs in somatic (body) cells   Occurs only...
DNA Replication• A process where DNA duplicates itself during  interphase• Also called semi conservative replication  – Ha...
Meet the proteins!                                                                      DNA Ligase:Helicase:              ...
Process of DNA replication                http://www.mcb.harvard.edu/losick/images/trombonefinald.swf
Alcohol metabolism causes DNA damage and triggers a breast cancer-    related DNA damage response• Ethanol is carcinogenic...
• 30% of East Asians are unable to metabolise  alcohol to acetate due to a genetic variant in  the ALDH2 gene• Increased r...
Bibliography•   Albert, B. et al., 2010. Essential Cell biology. 3rd ed. New York, NY: Garland    Science.•   Becker,W.M.,...
•                                  Photo Credits    http://creationrevolution.com/2010/10/things-just-don%E2%80%99t-float-...
Photo Credits•   http://www.sivabio.50webs.com/mus.htm•   http://www.cytochemistry.net/cell-biology/actin_filaments_intro....
The cytoskeletal system, cell cycle and dna(project)
The cytoskeletal system, cell cycle and dna(project)
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The cytoskeletal system, cell cycle and dna(project)

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  • Intricate-complicated/complexThe cytoskeleton is not only the “bones” of a cell, but its “muscles” tooThe ability of eukaryotic cells to adopt a variety of shapes, organise the many components in their interior, interact mechanically with the environment, and carry coordinated movements depends on the cytoskeleton
  • Establishing cell shape & mechanical strength-support large amounts of cytoplasm in a eukaryotic cell – a function particularly important in animal cells (why?)Locomotion-Directly responsible for large-scale movements such as the crawling of cells along a surface, contraction of muscle cells and the changes in cell shape that takes place as an embryo develops.Intracellular transport-The cytoskeleton controls the location of the organelles that conducttheir specialised functions
  • A family of fibrous proteins form the intermediate filamentsTubulin is the subunit of microtubulesActin is the subunit of actin filaments
  • INTERMEDIATE because thin actin 8, thick micro 25, so it’s in the middle!Non-ionic detergents-detergents with a high micelle molecular weightUSED IN DISH-WASHING LIQUIDS.A class of synthetic detergents in which the molecules do not ionise in aqueous solutionsOrganic compundNON-IONIC:UNCHARGED AND HYDROPHILIC HEAD GROUPS, WITH HYDROPHOBIC TAILS
  • Plectin : hold together bundles of IF and link IF to microtubles,actin filaments an demosomes (cell-cell junctions)
  • 1-3 in cytoplasm4 in cell nucleusGlial cells- non-neural cells that supports neurons by providing support and nutrientsA type of glial cell-schwann cells10-50x more glial cells than neurons in the brain
  • By the time they reach their teensMutation of gene that encodes for Lamin A
  • Centrosome :The organelle located near the nucleus in the cytoplasm that divides and migrates to opposite poles of the cell during mitosis, and is involved in the formation of mitotic spindle, assembly ofmicrotubules, and regulation of cell cycle progression; the region pertaining to the organelle.2 types differ in structural stability and degree of organisation.
  • Cell cortex: specialized layer of cytoplasm on the inner face of the plasma membrane that functions as a mechanical support of the plasma membraneOther functions: cell streaming , cell division, maintenance of cell shape
  • Sister chromatid: each identical copy of a single chromosomeCentrosomes make a duplicate of itself
  • Short strand of RNA serves as a primer for DNA synthesis
  • Alcohol metabolism product, acetaldehyde, causes DNA replication to ceaseFindings not strong enough to prove alcohol directly causes cancer in humansScientists did a study of effect of alcohol on human cellsFound out that cells responded to DNA damage by activating FA-BRCA network (a collection of proteins) to protect cells against carcinogenic damage by coordinating DNA repair or helping replication machinery to bypass DNA damage-protects against breast cancer
  • The cytoskeletal system, cell cycle and dna(project)

    1. 1. The cytoskeletal system, cell cycle and DNA replication Hilary Mok Yolande Leong BMS/1M02 Cheesecake!
    2. 2. The Cytoskeletal System• An intricate network of protein filaments that extend throughout the cytoplasm• Highly dynamic->continuously reorganised as a cell changes shape, divides and responds to its environment
    3. 3. Functions of the cytoskeleton• Establishes cell shape• Provides mechanical strength• Locomotion• Chromosome separation in mitosis and meiosis
    4. 4. Components of cytoskeletal system1. Intermediate Filaments2. Microtubules3. Actin Filaments• Each type of filament has distinct mechanical properties and is formed from a different protein subunit.• Thousands of these subunits come together to form a fine thread of protein
    5. 5. Intermediate filaments (IF)• 8-10nm• Strong and Rope-like• Form a network throughout the cytoplasm of most animal cells• Toughest and most durable of the three• Can survive concentrated salt solutions and non-ionic detergents
    6. 6. Functions & Properties of IF• Have great tensile strength for structural support• Strengthens cells against mechanical stress when stretched• Maintenance of animal cell shape• Stabilised and reinforced by accessory proteins (e.g. plectin)
    7. 7. Categories of IF Intermediate Filaments Cytoplasmic Nuclear Vimentin and Keratins Vimentin-related Neurofilaments Nuclear Lamins filaments In (mostly) In connective In nerve cells In all animal cellsepithelial cells tissue, muscle cells and glial cells
    8. 8. Cytoplasmic IF• Keratin – Span interiors of epithelial cell from one side to the other – Forms a cable of high tensile strength which distributes stress exerted on the skin cell• Vimentin and Vimentin-related filaments – Maintain cell shape for glial cell – Provide structure support for contractile machinery• Neurofilaments – Supports axon growth
    9. 9. Nuclear IF• Nuclear lamina – Just beneath nuclear membrane – Underlies and strengthens the nuclear envelope in all eukaryotic cells – Other types extends across the cytoplasm, giving cells mechanical strength
    10. 10. Hutchinson-Gilford Progeria Syndrome (HGPS) • Caused by mutation of gene that encodes for Lamin A • Not hereditary • Rare and fatal condition, no cure • Cell nucleus has aberrant morphology as compared to a normal cell nucleus
    11. 11. • Affects children of all ethnicity• Cause individuals to appear to age prematurely• Signs: growth failure, loss of body fat and hair, wrinkled skin, stiffness in joints, atherosclerosis, stroke• Patients die young, ranging from 8-21, averaging at 13
    12. 12. Ashley Hegi, 16
    13. 13. Microtubules• Long, hollow cylinder , made from the protein tubulin• 25nm in diameter• More rigid than actin filaments• Normally have one end attached to a centrosome.• 2 types : Axonemal microtubules and Cytoplasmic microtubules
    14. 14. Axonemal microtubules• Highly organised, stable microtubules in specific subcellular structure associated with cellular movements (E.g. cilia, flagella)
    15. 15. Cytoplasmic microtubules• Loosely organised, dynamic network of microtubules• Variety of functions: formed mitotic and meiotic spindles, required from movements of chromosomes during mitosis and meiosis• Provides an organised system of fibres to guide movements on vesicles and other organelles
    16. 16. Actin Filaments (Microfilaments)• 2-stranded helical polymers of the protein actin• Thin and flexible structure, diameter 5 - 9nm• Generally unstable• Can form stable structure when associating with other actin-binding proteins• Perform a variety of functions depending on the protein it associated with
    17. 17. 2 main functions of Actin filaments• Muscle contraction
    18. 18. 2. Cell locomotion (“crawling”)E.g. amoebae
    19. 19. Cell Cycle• Duplication and division• Essential mechanism by which all living things reproduce• Details vary from one organism to another, occur at different times• Interphase (G0, G1, S and G2 phase) , M phase (mitosis) and C phase (cytokinesis)
    20. 20. Cell cycle control system• Ensures that events of the cell cycle (DNA replication, mitosis, etc) occur in a set sequence and that each process has been completed before the next begins• Achieved by means of molecular brakes that can stop the cycle at various checkpoints: G1, G2, M (mitosis)
    21. 21. M phase (Mitosis)• A process of nuclear division• Replicated copies of a cell’s DNA are organised into chromosomes• Identical copies of the DNA are then divided equally between 2 daughter cells• Five stages: Prophase, Prometaphase, Metaphase, Anaphase and Telophase
    22. 22. Prophase• Replicated chromosomes consisting of 2 closely associated sister chromatids condense• Nuclear envelope breaks down• Spindle fibres form as microtubules grow out of the centrioles that move to opposite ends of the cell
    23. 23. Prometaphase• Starts abruptly with the breakdown of the nuclear envelope• Chromosomes attach to spindle microtubules via their kinetochores and undergo active movement
    24. 24. Metaphase• Kinetochores of the chromosomes line up along the equator of the cell, moved by the spindle microtubules• The spindle is now fully formed and the microtubules attach to each sister chromatid
    25. 25. Anaphase• Begins when the sister chromatids synchronously separate• Centromere holding sister chromatids together divides• Kinetochore microtubules get shorter and spindle poles move apart, both contributing to chromosome segregation
    26. 26. Telophase• 2 groups of chromosomes reach the opposite poles of the spindle• As a new nuclear envelope starts to form around each group of chromosomes, they uncoil and the spindle disappears• Division of the cytoplasm begins with the assembly of the contractile ring
    27. 27. C phase (cytokinesis)• Division of cytoplasm and organelles• Cytoplasm is divided into 2 by a contractile ring of actin and myosin filaments• Cleavage furrow forms by action of contractile ring• Causes a pinch in the cell to create 2 daughters, each with a nucleus
    28. 28. Meiosis I (reduction division)
    29. 29. Meiosis II (separation division)
    30. 30. Difference between Mitosis and MeiosisMitosis MeiosisOccurs in somatic (body) cells Occurs only in reproductive (sex) cellsDiploid (2n) Haploid (n)2 daughter cells (diploid) 4 daughter cells (haploid)One cell division Two cell divisionsGenetically identical Genetically different
    31. 31. DNA Replication• A process where DNA duplicates itself during interphase• Also called semi conservative replication – Half of parent molecule retained by each daughter molecule
    32. 32. Meet the proteins! DNA Ligase:Helicase: Joins the gaps DNA Polymerase III: Single-strand DNAUses energy from between newly Core replication Binding Protein:ATP hydrolysis to synthesised DNA enzyme of the cell Binds to single-unwind DNA (Okazaki) stranded DNA fragments DNA Polymerase Sliding Clamp: DNA Primase: Removes the RNA Beta subunit of DNA An RNA polymers that primer and Polymerase III; encircles generates a short RNA replaces it with and slides along the DNA primer DNA (oligoribonucleotide)
    33. 33. Process of DNA replication http://www.mcb.harvard.edu/losick/images/trombonefinald.swf
    34. 34. Alcohol metabolism causes DNA damage and triggers a breast cancer- related DNA damage response• Ethanol is carcinogenic to human cells at several sites in the body• Alcohol metabolism product, acetaldehyde causes DNA damage, chromosomal abnormalities and acts as an animal carcinogen• Acetaldehyde acetate (relatively harmless)• By enzyme aldehyde dehydrogenase2 (ALDH2)
    35. 35. • 30% of East Asians are unable to metabolise alcohol to acetate due to a genetic variant in the ALDH2 gene• Increased risk of oesophageal cancer from alcohol consumption• findings show cells responded to DNA damage by activating Fanconi anemia-breast cancer (FA-BRCA) network –protects against breast cancer
    36. 36. Bibliography• Albert, B. et al., 2010. Essential Cell biology. 3rd ed. New York, NY: Garland Science.• Becker,W.M., Lewis,J.K. and Hardin,J., 2006. The World Of The Cell. 6th ed. San Francisco, CA: Pearson Education.• Alcoholism: Clinical & Experimental Research (2011, September 15). Alcohol metabolism causes DNA damage and triggers a breast cancer-related DNA damage response.ScienceDaily. Retrieved November 29, 2011, from http://www.sciencedaily.com-/releases/2011/09/110915163508.htm• http://www.biology-online.org/dictionary/Centrosome• http://highered.mcgraw- hill.com/sites/0072495855/student_view0/chapter2/animation__mitosis_and_cyt okinesis.html• http://highered.mcgraw- hill.com/sites/0072495855/student_view0/chapter2/animation__how_the_cell_cy cle_works.html• http://biology.about.com/od/mitosis/ss/mitosisstep_2.htm• http://www.mcb.harvard.edu/losick/images/trombonefinald.swf• http://www.medicalnewstoday.com/articles/146746.php
    37. 37. • Photo Credits http://creationrevolution.com/2010/10/things-just-don%E2%80%99t-float-around-simple-cell-part-3/• http://www.readengage.com/articles/s4.php• http://www.matthewmancuso.com/uncategorized/more-presentations-and-the-nbtc-short-course-on-cell- culture/• http://www.ncbi.nlm.nih.gov/books/NBK28434/bin/ch16f12.jpg• http://liquidbio.pbworks.com/w/page/11135254/Kasra%20Manoocheri%20Organelles%20Project• http://www.bionalogy.com/morphogenesis.htm• http://life-inspired.blogspot.com/2010/10/links-for-lecture-12.html• http://publications.nigms.nih.gov/insidethecell/chapter1.html• http://www.flickr.com/photos/yukilife/6325546825/• http://www.glogster.com/adasilva/chapter-10-bio/g- 6nvv1io6uqivcehd83gmd6p?old_view=Truehttp://www.guardian.co.uk/science/2010/nov/23/william-astbury- dna-scientist• http://www.medicalnewstoday.com/articles/146746.php• http://home.ccr.cancer.gov/inthejournals/Hernandez.asp• http://scienceblogs.com/transcript/2006/08/whats_inside_of_a_microtubule.php• http://taksreview.wikispaces.com/Mitosis• http://www.nature.com/nrm/journal/v10/n11/fig_tab/nrm2782_F4.html• http://www.sivabio.50webs.com/mus.htm• http://www.cytochemistry.net/cell-biology/actin_filaments_intro.htm• http://emartino76.wordpress.com/cp-biology/• http://apbiologydodd.wikispaces.com/Meiosis• http://scienceblogs.com/transcript/2006/08/whats_inside_of_a_microtubule.php• http://www.nature.com/nrm/journal/v10/n11/fig_tab/nrm2782_F4.html
    38. 38. Photo Credits• http://www.sivabio.50webs.com/mus.htm• http://www.cytochemistry.net/cell-biology/actin_filaments_intro.htm• http://www.mcb.harvard.edu/losick/images/trombonefinald.swf• http://notesforpakistan.blogspot.com/2010/09/microtubules-short- note.htmlhttp://www.cytochemistry.net/cell- biology/actin_filaments_intro.htmhttp://www.utm.utoronto.ca/~w3bio315/lecture12.htmhttps://b uffonescience9.wikispaces.com/UNIT+3+-+Cell+Reproduction• http://upload.wikimedia.org/wikipedia/commons/thumb/9/91/Anaphase_IF.jpg/300px- Anaphase_IF.jpg• http://www.wi.mit.edu/news/paradigm/spring_2008/splitsville.html• http://publications.nigms.nih.gov/insidethecell/ch4_interphase_big.html• http://www.ivy-rose.co.uk/HumanBody/Cells/Cell-Division_Mitosis-Diagram.php• http://chickscope.beckman.uiuc.edu/explore/embryology/day07/action.html• http://en.wikipedia.org/wiki/Metaphase• http://www.sciencephoto.com/media/214744/view• http://quizlet.com/4011656/spencer-unit-6-mitosis-flash-cards/• http://www.carolina.com/product/life+science/dvds+and+videos/basics+of+genetics- +cellular+reproduction-+mitosis,+cytokinesis,+and+the+cell+cycle+dvd.do• http://beholdmybeauty.com/keravitae.html• http://web.wi.mit.edu/matsudaira/pub/fimbrin.shtml
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