Presentation on theme: "Dispatch 1) Explain the structure and function of a chromosome 2) Copy and fill in Organism Diploid # (in somatic cells) Haploid # (in gametes) Cat Rose."— Presentation transcript:
1Dispatch1) Explain the structure and function of a chromosome 2) Copy and fill inOrganismDiploid # (in somatic cells)Haploid # (in gametes)CatRoseGoatRiceDogChimpanzees
4Mitosis in Action Spindle=_________ Nucleus=_________ Cell Membrane=______Chromosome=______
5In unicellular organisms, division of one cell reproduces the entire organism Multicellular organisms depend on cell division for:Development from a fertilized cellGrowthRepair
6Concept 12.1: Cell division results in genetically identical daughter cells Cells duplicate their genetic material before they divide, ensuring that each daughter cell receives an exact copy of the genetic material, DNAA dividing cell duplicates its DNA, allocates the two copies to opposite ends of the cell, and only then splits into daughter cells
7Cellular Organization of the Genetic Material A cell’s endowment of DNA (its genetic information) is called its genomeDNA molecules in a cell are packaged into chromosomes
8Every eukaryotic species has a characteristic number of chromosomes in each cell nucleus Somatic (nonreproductive) cells have two sets of chromosomesGametes (reproductive cells: sperm and eggs) have half as many chromosomes as somatic cellsEukaryotic chromosomes consist of chromatin, a complex of DNA and protein that condenses during cell division
9Distribution of Chromosomes During Cell Division In preparation for cell division, DNA is replicated and the chromosomes condenseEach duplicated chromosome has two sister chromatids, which separate during cell divisionThe centromere is the narrow “waist” of the duplicated chromosome, where the two chromatids are most closely attached
11Eukaryotic cell division consists of: Mitosis, the division of the nucleusCytokinesis, the division of the cytoplasmGametes are produced by a variation of cell division called meiosisMeiosis yields nonidentical daughter cells that have only one set of chromosomes, half as many as the parent cell
12Phases of the Cell Cycle The cell cycle consists ofMitotic (M) phase (mitosis and cytokinesis)Interphase (cell growth and copying of chromosomes in preparation for cell division)Interphase (about 90% of the cell cycle) can be divided into subphases:G1 phase (“first gap”)S phase (“synthesis”)G2 phase (“second gap”)
13INTERPHASE S (DNA synthesis) LE 12-5INTERPHASES(DNA synthesis)G1CytokinesisMitosisG2MITOTIC(M) PHASE
15The Mitotic Spindle: A Closer Look The mitotic spindle is an apparatus of microtubules that controls chromosome movement during mitosisAssembly of spindle microtubules begins in the centrosome, the microtubule organizing centerThe centrosome replicates, forming two centrosomes that migrate to opposite ends of the cell, as spindle microtubules grow out from themAn aster (a radial array of short microtubules) extends from each centrosome
17In anaphase, sister chromatids separate and move along the kinetochore microtubules toward opposite ends of the cellThe microtubules shorten by depolymerizing at their kinetochore ends
18Chromosome movement Kinetochore Tubulin subunits Motor Microtubule LE 12-8bChromosomemovementKinetochoreTubulinsubunitsMotorproteinMicrotubuleChromosome
19Cytokinesis: A Closer Look In animal cells, cytokinesis occurs by a process known as cleavage, forming a cleavage furrowIn plant cells, a cell plate forms during cytokinesisAnimation: Cytokinesis
20LE 12-9a100 µmCleavage furrowContractile ring ofmicrofilamentsDaughter cellsCleavage of an animal cell (SEM)
21LE 12-9bVesiclesformingcell plateWall ofparent cell1 µmCell plateNew cell wallDaughter cellsCell plate formation in a plant cell (TEM)
22LE 12-10 Chromatin condensing Nucleus Chromosomes Cell plate 10 µm NucleolusProphase. Thechromatin is condensing.The nucleolus is beginning to disappear.Although not yet visible in the micrograph, the mitotic spindle is starting to form.Prometaphase. Wenow see discrete chromosomes; eachconsists of two identical sister chromatids. Laterin prometaphase, thenuclear envelope will fragment.Metaphase. The spindle is complete, and the chromosomes, attached to microtubules at their kinetochores, are all atthe metaphase plate.Anaphase. Thechromatids of each chromosome have separated, and the daughter chromosomes are moving to the ends of the cell as their kinetochore micro-tubules shorten.Telophase. Daughter nuclei are forming. Meanwhile, cytokinesis has started: The cell plate, which will divide the cytoplasm in two, is growing toward the perimeter of the parent cell.
23Binary FissionProkaryotes (bacteria and archaea) reproduce by a type of cell division called binary fissionIn binary fission, the chromosome replicates (beginning at the origin of replication), and the two daughter chromosomes actively move apart
24Chromosome replication begins. Soon thereafter, LE 12-11_1Cell wallOrigin ofreplicationPlasmamembraneE. coli cellBacterialchromosomeChromosome replication begins. Soon thereafter,one copy of the origin moves rapidly toward the other end of the cell.Two copiesof origin
25Chromosome replication begins. Soon thereafter, LE 12-11_2Cell wallOrigin ofreplicationPlasmamembraneE. coli cellBacterialchromosomeChromosome replication begins. Soon thereafter,one copy of the origin moves rapidly toward the other end of the cell.Two copiesof originOriginOriginReplication continues. One copy of the origin is now at each end of the cell.
26LE 12-11_3 Cell wall Origin of replication Plasma membrane E. coli cellBacterialchromosomeChromosome replication begins.Soon thereafter,one copy of the origin moves rapidly toward the other end of the cell.Two copiesof originOriginOriginReplication continues. One copy of the origin is now at each end of the cell.Replication finishes.The plasma membrane grows inward, andnew cell wall is deposited.Two daughtercells result.
27The Cell Cycle Control System The sequential events of the cell cycle are directed by a distinct cell cycle control system, which is similar to a clockThe clock has specific checkpoints where the cell cycle stops until a go-ahead signal is received
30What is Cancer? Cancer means uncontrolled cell growth The body needs to keep cell growth = cell deathCell cycle checkpoints kill mutated or old cells
31Cell Cycle Checkpoints Mutated cancer cells skip cell cycle checkpoints at the end of:G1: Is the cell big enough?G2: Is the cell ready for mitosis?Mitosis: Does the body need more cells?
32G1 Phase S Phase Mitosis Cytokinesis G2 Phase The cell cycle has traffic lights that serve as checkpointsIs the cell big enough?G1 PhaseS PhaseMitosisCytokinesisG2 PhaseDoes the body need more cells?Is the cell ready for mitosis?
33Cancer is caused when the checkpoints are broken and the cell cycle keeps going without stopping G1 PhaseS PhaseMitosisCytokinesisG2 Phase
34What are the types of cancer? *Any part of the body can be cancerousSkin cancerLung cancerBreast cancerTesticular cancerColon cancerLiver cancerBrain cancerLung CancerBrain Cancer
36How do you get cancer? How can you get cancer? Getting hit in the breast?NOHaving unprotected sex?Smoking?YESBeing in the sun too long?
37Why is cancer so deadly? * 1) Mutated cells beat the cell cycle checkpoints and keep dividing2) They form tumors which then stop your body parts from functioning normally3) Angiogensis – the tumors hijack blood vessels to keep them alive4) Metastisis – the cells from the tumor travel and infect other parts of your body*
40Why is Cancer so Hard to Cure? It is a silent killer, by the time it is found it is already to late2) Chemo/Radiation therapy can kill cancer cells, but is hard on patients3) If one cancer cell survives, or travels, cancer will come back
41Can cancer be prevented? Cancer is not contagious.There is no guaranteed way to prevent cancer, people can reduce their risk (chance) of developing cancer by:A) not using tobacco productsB) choosing foods with less fat and eating more vegetables, fruits, and whole grainsC) exercising regularly and maintaining a lean weightD) avoiding the harmful rays of the sun, using sunblock, and wearing clothing that protects the skin
42G1 checkpoint Control system S G1 G2 M M checkpoint G2 checkpoint LE 12-14G1 checkpointControlsystemSG1G2MM checkpointG2 checkpoint
43For many cells, the G1 checkpoint seems to be the most important one If a cell receives a go-ahead signal at the G1 checkpoint, it will usually complete the S, G2, and M phases and divideIf the cell does not receive the go-ahead signal, it will exit the cycle, switching into a nondividing state called the G0 phase
44LE 12-15G0G1 checkpointG1G1If a cell receives a go-ahead signal at the G1 checkpoint, the cell continues on in the cell cycle.If a cell does not receive a go-ahead signal at the G1 checkpoint, the cell exits the cell cycle and goes into G0, a nondividing state.
45The Cell Cycle Clock: Cyclins and Cyclin-Dependent Kinases Two types of regulatory proteins are involved in cell cycle control: cyclins and cyclin-dependent kinases (Cdks)The activity of cyclins and Cdks fluctuates during the cell cycle
46Relative concentration LE 12-16aMG1SG2MG1SG2MMPF activityCyclinRelative concentrationTimeFluctuation of MPF activity and cyclin concentrationduring the cell cycle
47Molecular mechanisms that help regulate the cell cycle LE 12-16bG1CyclinSCdkDegradedcyclinMG2accumulationG2checkpointCdkCyclin isdegradedCyclinMPFMolecular mechanisms that help regulate the cell cycle
48Stop and Go Signs: Internal and External Signals at the Checkpoints An example of an internal signal is that kinetochores not attached to spindle microtubules send a molecular signal that delays anaphaseSome external signals are growth factors, proteins released by certain cells that stimulate other cells to divideFor example, platelet-derived growth factor (PDGF) stimulates the division of human fibroblast cells in culture
49LE 12-17 Scalpels Petri plate Without PDGF With PDGF Without PDGF 10 mm
50Another example of external signals is density-dependent inhibition, in which crowded cells stop dividingMost animal cells also exhibit anchorage dependence, in which they must be attached to a substratum in order to divide
51Cells anchor to dish surface and divide (anchorage dependence). LE 12-18aCells anchor to dish surface anddivide (anchorage dependence).When cells have formed a completesingle layer, they stop dividing(density-dependent inhibition).If some cells are scraped away, theremaining cells divide to fill the gap andthen stop (density-dependent inhibition).25 µmNormal mammalian cells
52Cancer cells exhibit neither density-dependent inhibition nor anchorage dependence
53Cancer cells do not exhibit anchorage dependence LE 12-18bCancer cells do not exhibitanchorage dependenceor density-dependent inhibition.25 µmCancer cells
54Loss of Cell Cycle Controls in Cancer Cells Cancer cells do not respond normally to the body’s control mechanismsCancer cells form tumors, masses of abnormal cells within otherwise normal tissueIf abnormal cells remain at the original site, the lump is called a benign tumorMalignant tumors invade surrounding tissues and can metastasize, exporting cancer cells to other parts of the body, where they may form secondary tumors
55LE 12-19 Lymph vessel Tumor Blood vessel Glandular tissue Metastatic Cancer cellA tumor grows from asingle cancer cell.Cancer cells invadeneighboring tissue.Cancer cells spreadthrough lymph andblood vessels toother parts of thebody.A small percentageof cancer cells maysurvive and establisha new tumor in anotherpart of the body.