2Cell Cycle Presentation By: Shaista Abid Botany department Dcw phase viii
3List of Contents Action Plan Cell Cycle Importance of Mitosis InterphaseG1 phaseS phaseG2 phaseM PhaseKaryokinesisMitosisProphasePrometaphaseMetaphaseAnaphaseTelophaseCytokinesisCell Plate FormationCell DepressionImportance of MitosisConclusionReferencesSummary
4Action Plan Cell Cycle and Mitosis For Class XII (P.M) By Shaista Abid DACW phase-VIII
5Long Term GoalsAdopt 21st century teaching approaches to enhance students skills.Must have information about media and technology savvy.Must be able to adopt the curriculum and the requirements to teach to the curriculum in imaginative ways.Must know the importance of social skills.
6Short Term GoalsMust be able to adopt to a dynamic teaching experience.As an educator must understand and apply different learning styles.Must be a best communicator.Develop critical thinking by changing questions.
7Instructional strategies and Task Content sequence and clustering.Learning components.Student groupings.Group discussion between students.Providing feedback about performance correctness.I try to follow content in the sequence.I try to learn students by questioning.I make a 4 students group during practical.I will make a group discussion to enhance their skills.I will appreciate them by good remarks.
8Solutions to Anticipated Challenges Power failure is the main problem through out the working.Computer is not available in the lab.There is no proper white screen for the projector.There is no sitting arrangement for multimedia class.Although generator is available but we some time have voltage problem.I do all my computer work at home.I use class room’s wall as a screen.Lab is used for this purpose.
9Time Line Cell Cycle 5 min 5 min 20 min 10 min M phase OR Mitosis Definition of Cell Cycle5 minPhases of Cell Cycle5 minM phase OR MitosisInterphase20 min10 minPhases of MitosisImportance of MitosisG1 phaseS phaseG2 phaseG0 phaseProphasePrometaphaseMetaphaseAnaphaseTelophase
10Cell Cycle Events of Cell Cycle Cell cycle:- The cell cycle is an ordered set of events, which occurs between the formation of a cell and its division into two daughter cells.Events of Cell CycleInterphaseG1 phaseS phaseG2 phaseM phaseInterphase + karyokinesis + cytokinese=Cell Cycle
11InterphaseDuring interphase, the cell is growing and preparing for mitosis (M phase) by accumulating nutrients and replicating DNA. Interphase is the longest phase in cell cycle. Though this phase is sometimes called resting stage, but it is in fact the most active phase of the cell cycle.It consists of following phases i.e.
12G1(gap 1) PhaseIn this phase daughter cells acquire ATP and increase in size. In this phase cytoplasmic growth occurs and the cell prepares its enzymatic machinery for S phase. No change in DNA amount or chromatin. Each chromosome contains only a single molecule of DNA. In G1 production of mitochondria, plastids, endoplasmic reticulum, lysosomes, golgi apparatus, vacuoles takes place. During G1 phase, a cell may follow one of the three options: 1. cell has reached the restriction point (R point). After a short rest it continue on the cycle and divide. 2. The cell permanently stop division and withdrawn from cycle and enter G0 or quiescent stage When conditions change and growth is resumed the cell re-enters the G1. G1 is typically the longest phase of the cell cycle. Cells usually remain in G1 for about 10 hours of the 24 total hours of the cell cycle
13S phaseDuring the S phase, new DNA is synthesized by the cell resulting in each chromosome with two molecules of DNA. The DNA content of the nucleus is doubled and proteins are synthesized. Double-helical DNA molecule is duplicated, making two strands of DNA that are exactly identical. Two newly formed DNA strands are attached together by specific proteins, at a short sequence of DNA (which is found on each double helix) and called a centromere. The number of chromosomes remain same as were present in the newly formed cell(1n or 2n) but each chromosome is changed from single stranded form to two stranded form. Duration of S phase: The length of S phase varies according to the total DNA that the particular cell contains. Usually, cells will take between 5 and 6 hours to complete S phase.
14G2(Gap 2) Phase:During the pre-mitotic gap phase (G2), synthesis of RNA and protein continues, but DNA synthesis stops. The mitotic spindle proteins are formed. During G2 phase chromatin begins to condense into the relatively compact structures called chromosomes . Duration of G2 phase: G2 is shorter, lasting only 3 to 4 hours in most cells. In sum, then, interphase generally takes between 18 and 20 hours. Mitosis, during which the cell makes preparations for and completes cell division only takes about 2 hours.
15M PhaseMitosis: Mitosis is the common method of nuclear division, followed by cytokinesis (cytoplasmic division). It usually occurs in vegetative or somatic cells therefore it is known as somatic division.In this division the mother cell produces two genetically identical daughter cells which resemble each other and also parent cell qualitatively and quantitatively.Process of mitosis is divided into1. Karyokinesis : this is the division of nucleus and it is further divided inot five phases i.e.i Prophaseii Prometaphaseiii Metaphaseiv Anaphasev Telophase2. Cytokinesis: division of cytoplasm.
16Classification of Eukaryotic Cell Division KaryokinesisMitosisProphasePrometaphaseMetaphaseAnaphaseTelophaseCytokinesisCell plate formationBy constriction
17Prophase At the beginning of prophase chromosomes appear as thin filamentous uncoiled structures.Chromosomes become coiled, shortened.Nucleoli disappear.Each chromosome longitudinally splits into two sister chromatids.The chromatids join together by centromeres.chromatids are attached to spindle tubules with the help of protein plates called kinetochores.The kinetochore is the actual site of the insertion of the spindle threads and is a permanent part of the chromosome.
18Prometaphase The nuclear membrane disintegrates. The chromosomes are attached to the spindles through their centromeres.The chromosomes move freely and proceed towards the equator.spindle fibers, form from centrosome.During interphase, the cell has one centrosome but just before prophase, the centrosome duplicates, producing a second centrosome. During prophase, microtubules radiate from each centrosome.Spindle fibers extend from the poles to the equator.The spindle apparatus forms, which moves the chromosomes .The two centrosomes move to the opposite poles of the nucleus.The microtubule from one pole may attach to the knietochore and the chromosome begins to move toward the other pole aligning the chromosomes at the equatorial plane.
19Meta phase There are also two types of nonkinetochore microtubules:- The chromosomes line up in one plane to form theChromosome lies in the middle of the spindle apparatus and is perpendicular to its axis.Only the centromere lies on the equatorial plate, while the chromosome arms (chromatids) are directed away from the equator.Smaller chromosomes are usually central in position whereas the larger ones are peripheralThere are also two types of nonkinetochore microtubules:-Some microtubules radiate from the centrosome toward the metaphase plate without attaching to chromosomes. Others are too short to reach the metaphase plate.Still others extened across the plate and overlap with nonkinetochore microtubules from the opposite pole of the cell.
20Anaphasecentromeres divide and the spindle apparatus starts pulling the kinetochores to the opposite poles.The daughter kinetochores move apart dragging the chromosomes ( each now a single strand) to the poles.Two cells begin to form. In anaphse the centromeres divide and two sister chromatids separate and move to the opposite ends of the cell.
21Telophase Now chromosomes reach the poles of the daughter cells. Chromosomes decondense (uncoil)Nuclear membrane reappears around daughter nuclei Spindle Fibers become disorganized. the spindle apparatus breaks downThe nucleolus reappearsThe cell pinches in the middle, beginning the formation of the two cells The new cell plate expanding centrifugally.
22CytokinesisIs the division of cytoplasm which starts during anaphase. Two cells are produced as this process continues. Cytokinesis may beCell plate formation:Dumb bell shape ( by constriction)Plant cells divide by formation of a new cell wall (cell plate ) between daughter nuclei .New wall is regulated by the phragmoplast which contains microtubules, actin filaments and membranes.Fusion of these vesicles gives rise to a membrane-bound compartment, the cell plate.The cell plate expands from the middle out (centrifugally) until it reaches the "zone of attachment" or division site on the mother cell wall.The places where vesicles of the cell plate fail to fuse, the cytoplasmic contact between the daughter cells is maintained. Such cytoplasmic channels are lined by plasma membrane to form plasmodesmata .
24IMPORTANCE OF MITOSISThe number of cells in a plant increases due to mitosis leading to growth.It results in the increase of size, shape and volume of plant parts.Asexual reproduction, regeneration and cell replacement: A number of plants propagate (vegetatively) by mitotic divisions of the cells. Regeneration of lost parts and cells replacement (tissue repair) occurs by mitosis in multicellular plants.As a result of mitosis, two nuclei are formed which have same number of chromosomes as the parent cell.Hereditary material is equally distributed between two daughter cells.Asexual reproduction, regeneration, healing of wounds and replacement of older cells are the gift of mitosis.
25ConclusionCell division is very important process to continue organisms’ life cycle.Mitosis is a somatic cell division which causes growth of a living body.Pattern of mitosis is fundamentally same in all cells.By the process of mitosis not only chromosomes replicate but all necessary cytoplasm constituents and organelles are divided between two daughter cells.No change in chromosome number.Mitosis is observed in all type of cells i.e. haploid, diploid or polyploidy.Mitosis usually occurs in vegetative or somatic cells.Hereditary material is equally distributed between two daughter cells.Regeneration, healing of wounds and replacement of older cells take place by mitosis.
26sUMMARYCell undergoes series of changes, which involve period of growth, replication of DNA, followed by cell division. This sequence of change is called cell cycle.Cell cycle comprises of two phases i.e. interphase which is a period of non-apparent division and M phase which is the period of division.Interphase or resting phase is divided into G1-phase, S-phase, and G2-phase.G1-phase is the period of extensive metabolic activity in which cell normally grows in size and synthesized enzymes.In S-phase DNA is synthesized and chromosomes number is doubled.G2-phase stores energy for chromosome movements, synthesized mitosis protein, RNA and microtubule sub units.M-phase is the division phase which consists of prophase, metaphase, anaphase and telophase.Cytokinesis take place, in animal cell a constriction or depression appears in the cytoplasm from outside to inside. While in plant cell cytokinesis take place with the appearance of cell plate.
27REFERENCES www.yahoo.com www.wikipedia.com www.biology.about.com Biology XII, Punjab Text Board Lahore.Biology XII, Sindh Text BookBoard JamshoroGCSE Biology By D.G. Mackean.