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Video #1: Generations-Mitosis & Meiosis In the mid 1800’s what did Pasteur, Lister do? In 1876, What did Walter Flemming do that provided better visualization of parts in the cell? What did he see & discover? 2. Chromosomes literally mean: “_______” 3. What is a centromere and what is its function? 4. What is a karyotype and what does it reveal? What are “homologous chromosomes”? 5. How many chromosomes do humans, fruit flies (Drosophila), horsetails, Toads, and pea plants have? 6. Name the business used in the 2nd segment to show the importance of mitosis. 7. Briefly explain what “grafting” is? 8. A complete cycle can be completed in about ______hrs in a rapidly dividing tissue such as bone marrow. During this time mitosis occurs for only _______ hr(s). Pg. 221 9. Name the FOUR phases of Mitosis and two key events that occur. (See pg. 222-223) 10. Name two differences between Mitosis & Meiosis after watching the final segment. ****Write the Title for each segment and THREE key statements for each segment. 1. Introductory Questions #1 1) How much DNA does a typical human cell have? How are chromosomes differ from chromatin? 2) How is a somatic cell different from a gamete? 3) How is every species different in regards to their chromosomes? 4) Name the main stages of the cell cycle. (pg. 221) 5) What are the four stages of mitosis? Which stage is the longest and which stage is the shortest? 6) Give three specific events that occur during prophase. How is Prometaphase different from prophase? 7) How are plant cell different from animal cells when they divide? Introductory Questions #2 1) What are the three checkpoints of the cell cycle that regulates mitosis? Which one is considered the “restriction point”? Why this checkpoint and not the others? 2) Name the two protein molecules that are high in concentration during the mitotic (M) phase of the cell cycle. Name the complex that it forms. 3) Why are telomeres considered to be a “mitotic clock”? DO telomeres contain genes? What does telomerase do? (see pgs 306-307 in Ch. 16) 4) How are tumor supressor genes different from an oncogenes? How is a proto-oncogene different from an oncogene? What kind of a protein does the RAS gene produce? 5) What is the difference between a malignant tumor and a benign tumor? 6) When looking at the hypothetical sequence of how mitosis may have evolved how is the process different in a bacteria and diatom from a plant and animal cell? Introductory Questions #3 1) 2) 3) 4) 5) 6) 7) How is a totipotent stem cell different from a pluripotent stem cell? See pgs. 415-418 (Ch. 21) Which phase is used to obtain pictures of chromosomes in order to generate a karyotype Give five differences between Mitosis and Meiosis. Name three factors in Meiosis & reproduction that contributes in increasing genetic variability within a population. What is a polar body? How is oogenesis different from spematogenesis? How is a sporophyte different from a gametophyte? What do they produce and what process is involved, mitosis or meiosis? What is a tetrad? Which phase of Meiosis does crossing over occur? Mitosis and Meiosis • Chapter 12 & 13 • Mitosis & Meiosis Next Unit: Genetics & DNA • Chapter 12 & 13: Mitosis & Meiosis • Chapter 14: Principles of Heredity • Chapter 15: Human Genetics & Disorders • **Two Labs will be done for this Unit • Goal: to complete before Thanksgiving and to take Test #3 on 11/25 (Tuesday) Mitosis • Occurs only in certain types of cells • Form of asexual reproduction • Produces two genetically identical cells from one cell. • The splitting or dividing of the nucleus • Viewed in different stages by examining chromosome formation and behavior. Significance of Understanding Mitosis • Preserves the continuity of life • Allows organisms to grow, repair, and reproduce • Important in unlocking the mysteries of embryonic development & stem cells • Important in understanding how cancer develops and could someday provide clues in stopping cancer. • Cell replacement (seen here in skin) Dead cells Epidermis, the outer layer of the skin Dividing cells Dermis Figure 8.11B Packaging of Genetic Material http://www.biostudio.com/demo_freeman_dna_coiling.htm • • • • • • Structure / Activity Diameter DNA: smallest structure about (2 nm) DNA & Histones = Nucleosome (10 nm) Chromatin Fibers** (30 nm) Extensive Looping (300 nm) Further Condensing (700 nm) Fully Formed Chromosome (1400 nm) Chromosomes • Condensed DNA attached to proteins • Can only be seen when a cell is actively undergoing mitosis. • Typical humans form 46 chromosomes vs. other organisms which varies significantly. • Our 46 chromosomes are thought to contain anywhere from 25,000 to 100,000 genes. • Duplicated before mitosis occurs producing a sister chromatid (identical copy) • Sister chromatids held together by “Centromere” Cells from an onion Root tip • When the cell cycle operates normally, mitotic cell division functions in: – Growth (seen here in an onion root) Figure 8.11A • E. coli dividing Figure 8.3x • Asexual reproduction (seen here in a hydra) Figure 8.11C MITOSIS • A eukaryotic cell has many more genes than a prokaryotic cell – The genes are grouped into multiple chromosomes, found in the nucleus – The chromosomes of this plant cell are stained dark purple Figure 8.4A • Human male bands Figure 8.19x3 • Human female karyotype Figure 8.19x2 Sister chromatids • Before a cell starts dividing, the chromosomes are duplicated Centromere – This process produces sister chromatids Figure 8.4B • When the cell divides, the sister chromatids separate Chromosome duplication Sister chromatids Centromere – Two daughter cells are produced – Each has a complete and identical set of chromosomes Chromosome distribution to daughter cells Figure 8.4C Interphase Interphase • • • • • • Cells spend most of its time in this phase Cells are growing DNA has to be replicated (all 2 meters of it) Proteins are being produced 90% of all cells are in this phase Three phases: G1, S, and G2 Prophase Prophase • Chromatin thickens (coils) into chromosomes • Two copies of DNA are present: sister chromatids (twice the amount of DNA is present) • Centrioles replicate forming another centrosome separate. • Centrioles separate to each side of the nucleus • Nuclear membrane (envelope) disappears • Microtubules elongate forming the spindle apparatus Metaphase Metaphase • Chromosomes align themselves up in the center of the cell • Spindle fibers (microtubules) attach to the centromere of the chromosomes • Longest phase of Mitosis Metaphase • Mitotic spindle Figure 8.6x2 Anaphase - Early & Late Anaphase • Chromosomes separate by the shortening of the microtubules. • The sister chromatids separate to each side (pole) of the cell. (humans: 46 to each side) • The centrosome is located at each side of the cell. Telophase (Plant & Animal) Cytokinesis: Plant vs Animal Cells • Cleavage furrow: animals cells • Cell plate: Plant cells Cytokinesis differs for plant and animal cells • In animals, cytokinesis occurs by cleavage – This process pinches the cell apart Cleavage furrow Cleavage furrow Figure 8.7A Contracting ring of microfilaments Daughter cells • In plants, a membranous cell plate splits the cell in two Cell plate forming Wall of parent cell Cell wall Figure 8.7B Vesicles containing cell wall material Daughter nucleus New cell wall Cell plate Daughter cells Cells from an onion Root tip • When the cell cycle operates normally, mitotic cell division functions in: – Growth (seen here in an onion root) Figure 8.11A Whitefish-phases of Mitosis Various phases of Mitosis-Plants Which Phase is this? • Sea urchin development Figure 8.0x • Cell cycle collage Figure 8.5x • Fibroblast growth Figure 8.8x Total Class Data for all Three Classes: Fall 2005 Interphase Prophase Metaphase Anaphase Telophase Total # of cells 11806 2451 386 264 516 % in each phase 77% 16% 3% 2% 3% Time in each phase (min) 1102.3 228.8 36.0 24.6 48.2 Hours 18.4 3.8 0.6 0.4 0.8 Total Class Data for all Three Classes: Fall 2006 Interphase Prophase Metaphase Anaphase Telophase Total # of cells % in each phase Time in each phase (min) Hours 18296 84% 1208.1 20.1 1821 8% 122.3 2.0 529 2% 35.2 0.6 461 2% 29.9 0.5 695 3% 44.5 0.7 The Cell Cycle: Generation Time • Interphase: most of a cell’s life (90%) -G1: 1st gap of growth -S phase: DNA is duplicated (synthesized) -G2 phase: 2nd gap of growth • Mitosis: splitting of the nucleus (PMAT) • Cytokinesis: separation of the cytoplasm The cell cycle multiplies cells • The cell cycle consists of two major phases: – Interphase, where chromosomes duplicate and cell parts are made – The mitotic phase, when cell division occurs Figure 8.5 See Pgs 222-223 INTERPHASE PROPHASE Prometaphase Figure 8.6 METAPHASE ANAPHASE Cleavage furrow Metaphase plate Spindle TELOPHASE AND CYTOKINESIS Daughter chromosomes http://highered.mcgraw-hill.com/sites/0072437316/student_view0/chapter11/animations.html# Nuclear envelope forming Nucleolus forming The Kinetochores • Located in the middle of each sister chromatid. • Microtubules attach and breakdown as the sister chromatids are pulled to opposite sides of the cell. • See Research on Pg. 225 • Mitosis collage, light micrographs Figure 8.6x1 Evolution of Mitosis (pg. 227) Chromosomes attach to the plasma membrane Chromosomes attach to the nuclear membrane Pass through the nucleus Spindle forms within the nucleus Regulation of Cell Division • Driven by specific molecular signals • Research has shown: – Two cells in different phases causes the other to be pushed into the next phases. – Ex. • S phase & G1 grown together will cause the G1 cell to enter into the S phase immediately • M phase cell & G1 cell will cause the G1 cell to enter into the M phase immediately. • There is an obvious control system in place. Regulating Mitosis-Control System (pg. 229-231) • Most cells can divide up to 50 times • Control of the Cell cycle involves three checkpoints -G1 (most important checkpoint) = restriction point (G0: non-dividing state) -G2 -M phase • Growth factors (proteins): Cyclins & Kinases – Kinases: phosphorylate proteins, gives the go ahead – Cdk: are kinases that must be attached to a cyclin to be activated – MPF: Maturation promoting factor (Fig: pg. 230) • Complex of kinase and cyclin • Triggers the passage from G2 phase into M phase • peaks during Metaphase Growth factors signal the cell cycle control system • Proteins within the cell control the cell cycle – Signals affecting critical checkpoints determine whether the cell will go through a complete cycle and divide G1 checkpoint Control system M checkpoint G2 checkpoint Figure 8.9A Cyclin & Kinase effects on the cell cycle. • Animated link: http://nobelprize.org/educational_games/m edicine/2001/cellcycle.html Video #2: Cancer and its Causes Reference Pages: Ch. 16 Pgs. 306-307 Ch. 19 pgs. 370-373 ****While watching the video be sure to have a minimum of 15 key statements. Some of your statements should address: 1. What was thought to be the cause of cancer in the earlier years? What do we know today in regards to the causes of cancer? 2. Differences between an Oncogene and a Tumor suppressor gene and what these genes specifically do. 3. The RAS gene and p53 gene and what they do. Which one is a proto-oncogene 4. Why is the p53 gene considered to be the “Guardian Angel of the cell” Give three things that is does. 5. How has the study of Telomeres and the enzyme Telomerase contributed to our knowledge of cancer. Cyclin & MPF Concentrations • The binding of growth factors to specific receptors on the plasma membrane is usually necessary for cell division Growth factor Plasma membrane Receptor protein Signal transduction pathway Figure 8.8B Relay proteins G1 checkpoint Cell cycle control system Growth Factors that stimulate Cell Division PDGF: Platelet-derived growth factor causes fibroblasts to divide in response to an injury. Has been shown to be effective in artificial conditions Cytokinins: key hormone in plants that promotes cell division Mitotic Clock Mechanisms in Cells Telomeres, Proteins, Cell size (SA), hormones, & Growth factors • Telomeres: Segments of DNA (200 repeated sequences of nucleotides) are lost at the tips of the chromosomes with each mitotic event. – (Mitotic clock) the tips of chromosomes wear down and lose DNA sequences over time. – Six Nucleotide sequence repeated hundreds of times – 1,200 nucleotides are removed after each mitotic event Image of Telomeres-notice light Blue Regions Chromosomes in green & Telomeres in yellow Genes that are thought to cause Cancer See Pgs: 371-372 • Oncogenes: a gene that increases cell division and triggers cancerous characteristics. • Tumor Suppressor genes: a gene that inactivates or inhibits cell division. Prevents uncontrolled cell growth (cancer). It keeps mitosis in check and controls the cell cycle. • Failure of normal cell programmed death (Apotosis) Pgs. 800 & 902 Anchorage, cell density, and chemical growth factors affect cell division • Most animal cells divide only when stimulated, and others not at all • In laboratory cultures, most normal cells divide only when attached to a surface – They are anchorage dependent • Cells continue dividing until they touch one another – This is called density-dependent inhibition Cells anchor to dish surface and divide. When cells have formed a complete single layer, they stop dividing (density-dependent inhibition). If some cells are scraped away, the remaining cells divide to fill the dish with a single layer and then stop (density-dependent inhibition). Figure 8.8A • Growth factors are proteins secreted by cells that stimulate other cells to divide See pg. 232 After forming a single layer, cells have stopped dividing. Providing an additional supply of growth factors stimulates further cell division. Figure 8.8B • Malignant tumors can invade other tissues and may kill the organism Lymph vessels Tumor Glandular tissue Metastasis 1 A tumor grows from a single cancer cell. Figure 8.10 2 Cancer cells invade neighboring tissue. 3 Cancer cells spread through lymph and blood vessels to other parts of the body. Growing out of control, cancer cells produce Malignant tumors • Cancer cells have abnormal cell cycles – They divide excessively and can form abnormal masses called tumors • Radiation and chemotherapy are effective as cancer treatments because they interfere with cell division • Breast cancer cell Figure 8.10x1 • Mammograms Figure 8.10x2 Anti-Cancer drugs • Colchicine: blocks microtubules from forming -binds & inhibits unpolymerized tubulin -breakdown of microtubules occur -polyploidy could occur • Taxol: Found in the bark of yew trees -blocks ovarian cancer from forming http://www.ncl.ox.ac.uk/quicktime/taxol.html Video #2: Cancer and its Causes Reference Pages: Ch. 16 Pgs. 306-307 Ch. 19 pgs. 370-373 ****While watching the video be sure to have a minimum of 15 key statements. Some of your statements should address: 1. What was thought to be the cause of cancer in the earlier years? What do we know today in regards to the causes of cancer? 2. Differences between an Oncogene and a Tumor suppressor gene and what these genes specifically do. 3. The RAS gene and p53 gene and what they do. Which one is a proto-oncogene 4. Why is the p53 gene considered to be the “Guardian Angel of the cell” Give three things that is does. 5. How has the study of Telomeres and the enzyme Telomerase contributed to our knowledge of cancer. Lab #7-Rooting for Mitosis Objective & goals: Prepare and mount a slide of onion root cells in hopes of viewing and identifying the phases of Mitosis. -Cut off a approx. 1mm section of root tissue from rounded tip of the root. -One drop of 1M HCl & let stand for 4 min. -Use a tissue or towel to wick up the acid. -Cover the root tip with 1% Toluidine-set for 2 min. -Blot around root and rinse several times by absorbing with towel and rinsing with water until the water runs clear. -Add one drop of water and place a cover slip on the sample -Apply pressure & squash the tissue with your fingers or easer end of a pencil. Be careful not to crack the cover slip or slide. -View under the microscope first with low power then high power. -Identify, draw and label the phases observed in your sample. Lab #7 Part II: Viewing the Phases of Mitosis in Professionally Prepared slides of Allium (onion) root tip and Whitefish Blastula **Look for all the phases of mitosis including interphase using the prepared slides of plant and animal cells. **Count how many cells are in each phase and write those counts in table (#13) **Draw & LABEL all key structures: cell (plasma) membrane, nuclear membrane, chromosomes, nucleolus, and all phases: I P M A T IMPORTANT NOTE: Be sure to find a region on the root tip that has all the phases represented. This means one drawing for the onion root and one for the whitefish blastula. **Be sure to indicate the magnification, and source of the tissue (label on the slide) Finally: Find some images for these two tissues. Print and paste next to your drawing. Again be sure to include all labels you had in your drawing. Answer the Evaluation & Test Preparation Questions. Do the online quiz from the website written on your lab (after quest. #6) Stem Cells (pgs. 415-418) • Undifferentiated cells • Progenitor cells: partially specialized cell. an intermediate between a stem cell and a fully differentiated cell. • Pluripotent cells: follows fewer pathways that it can develop into. • Totipotent cells: cells that are very early in development when the zygote has developed into a small ball of cells. Cell Differentiation http://learn.genetics.utah.edu/units/stemcells/whatissc/ Heredity, Life Cycles, and Meiosis Chapter 13 Heredity Heredity: the transmission of traits from one generation to the next Asexual reproduction: clones Sexual reproduction: variation Human life cycle: 23 pairs of homologous chromosomes 1 pair of sex chromosomes (X or Y) and 22 pairs of autosomes; Karyotype : Pix of chromosomes -Gametes are haploid (n) -All other cells (somatic) are diploid (2n) -Fertilization (syngamy) joining (fusion) of gametes to produce a zygote Meiosis: cell division to produce haploid gametes • The human life cycle Haploid gametes (n = 23) Egg cell Sperm cell MEIOSIS FERTILIZATION Diploid zygote (2n = 46) Multicellular diploid adults (2n = 46) Mitosis and development Figure 8.13 Video #1: Generations-Mitosis & Meiosis In the mid 1800’s what did Paseur, Lister do? In 1876, What did Walter Flemming do that provided better visualization of parts in the cell? What did he see & discover? 2. Chromosomes literally mean: “_______” 3. What is a centromere and what is its function? 4. What is a karyotype and what does it reveal? What are “homologous chromosomes”? 5. How many chromosomes do humans, fruit flies (Drosophila), horsetails, Toads, and pea plants have? 6. Name the business used in the 2nd segment to show the importance of mitosis. 7. Briefly explain what “grafting” is? 8. A complete cycle can be completed in about ______hrs in a rapidly dividing tissue such as bone marrow. During this time mitosis occurs for only _______ hr(s). Pg. 221 9. Name the FOUR phases of Mitosis and two key events that occur. (See pg. 222-223) 10. Name two differences between Mitosis & Meiosis after watching the final segment. ****Write the Title for each segment and THREE key statements for each segment. 1. Alternative Life Cycles Fungi/some algae -Meiosis produces haploid cells (n) that divide by mitosis to produce -Haploid (n) adults (gametes produced by mitosis) Plants/some algae Do Alternation of generations: 2n = Sporophyte generation n = Gametophyte generation Meiosis occurs & produces spores: Spores are haploid (n) Spores divide by mitosis to generate more haploid cells (n) Gametes are produced by mitosis which then fertilize into a sporophyte (2n) Meiosis • Chromosome replicate • 2 Cell divisions occur (Meiosis I & Meiosis II) • 4 daughter cells are made all are (n): haploid • Homologous Chrom’s separate in meiosis I • Meiosis II = Mitosis (chromatids separate) Homologous chromosomes carry different versions of genes • The differences between homologous chromosomes are based on the fact that they can carry different versions of a gene (alleles) at corresponding loci Homologous Chromosomes (Are they identical?) Tetrad (Bivalent) ♂ from father from mother Sister Chromatids • Human female karyotype Figure 8.19x2 • Human male karyotype Figure 8.19x4 MEIOSIS I: Homologous chromosomes separate INTERPHASE Centrosomes (with centriole pairs) Nuclear envelope Figure 8.14, part 1 PROPHASE I METAPHASE I Microtubules attached to Spindle kinetochore Sites of crossing over Chromatin Sister chromatids Tetrad Metaphase plate Centromere (with kinetochore) ANAPHASE I Sister chromatids remain attached Homologous chromosomes separate Crossing over further increases genetic variability • Crossing over is the exchange of corresponding segments between two homologous chromosomes • Genetic recombination results from crossing over during prophase I of meiosis Tetrad Chaisma Centromere Figure 8.18A Synaptonemal Complex- Pg 213 • Protein that hold homologous chromosomes together • Thought to be involved in crossing over events Coat-color genes • How crossing over leads to genetic recombination Eye-color genes Tetrad (homologous pair of chromosomes in synapsis) 1 Breakage of homologous chromatids 2 Joining of homologous chromatids Chiasma 3 Separation of homologous chromosomes at anaphase I 4 Separation of chromatids at anaphase II and completion of meiosis Parental type of chromosome Recombinant chromosome Recombinant chromosome Parental type of chromosome Figure 8.18B Gametes of four genetic types Coat-color genes Eye-color genes Brown Black C E c e White Pink Tetrad in parent cell (homologous pair of duplicated chromosomes) Figure 8.17A, B C E C E c e c e Chromosomes of the four gametes Origins of Genetic Variation (1) Independent assortment: How they line up during metaphase I Matters!!! Homologous pairs of chromosomes position and orient themselves Randomly. (random positioning) Different combinations are possible when gametes are produced. POSSIBILITY 1 POSSIBILITY 2 Two equally probable arrangements of chromosomes at metaphase I Metaphase II Gametes Combination 1 Figure 8.16 Combination 2 Combination 3 Combination 4 Origins of Genetic Variation (2) Crossing over (prophase I): -the reciprocal exchange of genetic material between nonsister chromatids during synapsis of meiosis I (recombinant chromosomes) (3) Random fertilization: 1 sperm (1 of 8 million possible chromosome combinations) x 1 ovum (1 of 8 million different possibilities) = 64 trillion diploid combinations! MEIOSIS II: Sister chromatids separate TELOPHASE I AND CYTOKINESIS PROPHASE II METAPHASE II ANAPHASE II TELOPHASE II AND CYTOKINESIS Cleavage furrow Sister chromatids separate Figure 8.14, part 2 Haploid daughter cells forming Meiosis vs. Mitosis http://www.pbs.org/wgbh/nova/baby/divi_flash.html • Synapsis/tetrad/chiasmat a (prophase I) • Homologous vs. individual chromosomes (metaphase I) • Sister chromatids do not separate (anaphase I) • Meiosis I separates homologous pairs of chromosomes, not sister chromatids of individual chromosomes. MITOSIS MEIOSIS PARENT CELL (before chromosome replication) Site of crossing over PROPHASE I Tetrad formed by synapsis of homologous chromosomes PROPHASE Duplicated chromosome (two sister chromatids) METAPHASE ANAPHASE TELOPHASE 2n Daughter cells of mitosis Figure 8.15 Chromosome replication Chromosome replication 2n = 4 Chromosomes align at the metaphase plate Tetrads align at the metaphase plate Sister chromatids separate during anaphase Homologous chromosomes separate during anaphase I; sister chromatids remain together 2n MEIOSIS I METAPHASE I ANAPHASE I TELOPHASE I Haploid n=2 Daughter cells of meiosis I No further MEIOSIS II chromosomal replication; sister chromatids separate during anaphase II n n n n Daughter cells of meiosis II The End • Translocation Figure 8.23Bx • At fertilization, a sperm fuses with an egg, forming a diploid zygote – Repeated mitotic divisions lead to the development of a mature adult – The adult makes haploid gametes by meiosis – All of these processes make up the sexual life cycle of organisms • The large number of possible arrangements of chromosome pairs at metaphase I of meiosis leads to many different combinations of chromosomes in gametes • Random fertilization also increases variation in offspring • Human female bands Figure 8.19x1 • Human female karyotype Figure 8.19x2 • Human male bands Figure 8.19x3 • Human male karyotype Figure 8.19x4 • Down syndrome karyotype Figure 8.20Ax • Klinefelter’s karyotype Figure 8.22Ax • XYY karyotype Figure 8.22x