Cell Cycle & Control Points PDF

CELL CYCLE & Their Control Points  LEARNING COMPETENCY: Characterize the phases of the cell cycle and their control points STEM_BIO11/12-Id-f-6 REVIEW! How unspecialized cells became specialized to suit a specified function? Figure 1. Aging Concept of Humans from Birth to Adulthoo...

CELL CYCLE & Their Control Points  LEARNING COMPETENCY: Characterize the phases of the cell cycle and their control points STEM_BIO11/12-Id-f-6 REVIEW! How unspecialized cells became specialized to suit a specified function? Figure 1. Aging Concept of Humans from Birth to Adulthood 1.What process causes the formation of the different types of specialized cells? Consider the figure presented. 2.What do you think is the factor that causes specialized cells to increase in number which makes an organism grow? 3.Whenever a child got bruises or scratches while playing, how do cells repair from injuries?  Cells in multicellular organisms die in two ways. 1.necrosis. a cell may die by things that may harm them such as toxic chemicals or physical injuries.  2. apoptosis. cells are programmed or destined to die through apoptosis. example of a cell undergoing apoptosis is the red blood cell which has an approximate life span of 120 days  The Cell Cycle is an ordered sequence of events in the life of a cell, from its origin in the division of a parent cell until its own division into two. The division cycle of most cells consists of 4 coordinated processes: 1. cell growth, 2. DNA replication, 3. distribution of the duplicated chromosomes to daughter cells, and 4. cell division The Cell: A Molecular Approach. 2nd edition. Cooper GM.Sunderland (MA): Sinauer Associates; 2000. In bacteria, cell growth and DNA replication take place throughout most of the cell cycle, and duplicated chromosomes are distributed to daughter cells in association with the plasma membrane. The Cell: A Molecular Approach. 2nd edition. Cooper GM.Sunderland (MA): Sinauer Associates; 2000. In eukaryotes, the cell cycle is more complex and consists of four discrete phases. DNA is synthesized during only one phase of the cell cycle, and the replicated chromosomes are then distributed to daughter nuclei by a complex series of events preceding cell division. The Cell: A Molecular Approach. 2nd edition. Cooper GM.Sunderland (MA): Sinauer Associates; 2000. The Cell Cycle has three main phases: 1. Interphase 2. Mitosis (nuclear division, chromosome division) 3. Cytokinesis (cell division) -The time between cell divisions is the interphase. This is where cells spend most of their time -Mitosis and cytokinesis usually happen together  Interphase is divided into three (sometimes four) parts: 1. G1 (gap or growth phase 1) - Begins immediately after mitosis. RNA, protein, and other molecules are synthesized. This is basically the cell doing everything that is not associated with cell division.  The cell grows rapidly, while performing routine metabolic processes. It also makes proteins needed for DNA replication and copies some of its organelles in preparation for cell division. A cell typically spends most of its life in this phase.  Go - This stage can only be reached from G1. It is basically a pause in the cell cycle. Cells in G0 do not divide or undergo mitosis. Cells in G0 can return to G1 to continue the cell cycle.  2. S (synthesis)phase - The cell's DNA is replicated in the process of DNA replication. Chromosomes become duplicated.  3. G2 (gap or growth phase 2) -: During this phase, the cell makes final preparations to divide. For example, it makes additional proteins and organelles. Mitochondria (and chloroplasts) divide. Precursors of the spindle fibers are synthesized.  4. M Phase - mitosis actually occurs. replicated chromosomes and other cellular components are divided to ensure that each daughter cell receives equal distributions. The division of the cytoplasm at the end of the M phase is referred to as cytokinesis. Cell Division involves the distribution of identical genetic material or DNA to daughter cells. Cell Division functions in reproduction, growth, and repair. A typical eukaryotic cell cycle is illustrated by human cells in culture, which divide approximately every 24 hours However, mitosis and cytokinesis last only about an hour, so approximately how many percent of the time duration for interphase?..... Three major checkpoints are found in the G1, G2, and M phases of the Cell Cycle. Cell Cycle Checkpoints: A checkpoint is a stage in the eukaryotic cell cycle at which the cell examines internal and external cues and "decides" whether or not to move forward with division. Who are responsible for these checkpoints?  Cdk gene /Cyclin-Dependent Kinase group of genes that code for proteins called cyclin-dependent kinases (CDKs). These proteins are enzymes that play a crucial role in regulating the cell cycle. CDKs help control the transitions between the phases of the cell cycle The activating molecule is a cyclin, a protein that derives its name from its cyclically fluctuating concentration in the cell. Because of this requirement, these kinases are called cyclin- dependent kinases or CDKs Phosphorylating/phosphorylation biological process -phosphate grp + molecule(CHON) to activate/deactivate Phosphorylation is a chemical process of adding a phosphate group to an organic compound. Phosphorylation is essential for the functioning of proteins. I.The G1 Checkpoint—the Restriction Point The G1 checkpoint ensures that the cell is large enough to divide and that enough nutrients are available to support the resulting daughter cells. the primary pt. at which it must choose whether or not to divide FACTORS A CELL MIGHT ASESS: SIZE- Is the cell large enough to divide? NUTRIENTS- Does the cell have enough energy reserves or available nutrients to divide? MOLECULAR SIGNALS- Is the cell receiving positive cues (growth factors) from neighbors?. Is any of the DNA damaged?  If a cell receives a ‗go-ahead‘ signal at the G1 checkpoint, it will usually continue with the Cell Cycle. If the cell does not receive the go-ahead‘ signal, it will exit the Cell Cycle and switch to a non- dividing state called G0. Most cells in the human body are in the G0 phase. II.The G2 Checkpoint- ensures that DNA replication in S phase has been successfully completed. the cell will check: DNA integrity. Is any of the DNA damaged? DNA replication. Was the DNA completely copied S Phase Then………. halt & repair or…… apoptosis-programmed cell death III. The Metaphase Checkpoint/ Spindle checkpoint ensures that all of the chromosomes are attached to the mitotic spindle by a kinetochore TELOMERES Help protect the ends of chromosomes from degradation and prevent the loss of important genetic information ensures that the entire chromosomes is copied correctly How about the defense mechanism of the cell if there are abnormalities in the checkpoints? Proto-oncogenes The genes that code for the positive cell cycle regulators are normal genes that, when mutated in certain ways, become oncogenes, genes that cause a cell to become cancerous.  oncogenes play essential roles in regulating cell growth, division and repair but when: point mutation or amplifications ---promote uncontrolled proliferation----CA genes that have the potential to cause cancer when they undergo certain mutations or are overexpressed  Tumor Suppressor Genes are segments of DNA that code for negative regulator proteins, the type of regulators that, when activated, can prevent the cell from undergoing uncontrolled division. Rb, p53, and p21, is to put up a roadblock to cell cycle progression until certain vents are completed -Rb (Retinoblastoma Gene)- checkpoint(G1) , -p53 (TP53 Gene) -monitors DNA damage(initiate cell repair/ cell arrest (CA protection gene) -p21 (CDKN1A Genes-allows time for DNA repair...these genes play critical roles in regulating cell growth, cell cycle progression, and preventing the development of cancer  A normal cell divides about 50 times before its telomeres shorten to the point where the chromosome is risking damage on subsequent divisions.  Once the telomeres shorten to a threshold point, apoptosis (programmed cell death) occurs in the cell. Some cells have the ability to bypass cell death and thus become immortal. This is a key characteristic of cancer cells.  Cancer develops by a failure of a variety of mechanisms used to regulate progression through the cell cycle. Checkpoints exist throughout the cycle to ensure that cell division does not occur unless necessary. When these checkpoints are bypassed, cell division happens continually, ultimately producing a mass of unnecessary cells termed a tumor.  Cancer and the Cell Cycle “uncontrolled cell growth” All cancers start when a gene mutation gives rise to a faulty protein that plays a key role in cell reproduction. small uncorrected errors are passed from the parent cell to the daughter cells and amplified as each generation produces more non-functional proteins from uncorrected DNA damage.  Eventually, the pace of the cell cycle speeds up as the effectiveness of the control and repair mechanisms decreases. Uncontrolled growth of the mutated cells outpaces the growth of normal cells in the area, and a tumor (~oma) can result. APPLICATION:  How could the knowledge of the cell cycle be applied in developing proper assessment and treatments for cancer? Agriculture Genetic engineering Directions: Write numbers 1 – 6 on the space provided with number 1 corresponding to the first process and number 6 for the last process. __The cell replenishes its energy, stores, and synthesizes proteins necessary for chromosome manipulation. The cell grows in preparation for DNA replication. The nucleus of the cell divides. DNA is replicated which results in the formation of identical pairs of DNA molecules. The two daughter cells are produced. Cytokinesis or the division of the cytoplasm will occur. Directions: Write numbers 1 – 6 on the space provided with number 1 corresponding to the first process and number 6 for the last process. 3 The cell replenishes its energy, stores, and synthesizes proteins necessary for chromosome manipulation. 1 The cell grows in preparation for DNA replication. 4 The nucleus of the cell divides. 2 DNA is replicated which results in the formation of identical pairs of DNA molecules. 6 The two daughter cells are produced. 5 Cytokinesis or the division of the cytoplasm will occur. ASSIGNMENT Directions: Use a long-sized bond paper to accomplish this activity. Label the diagram below with the following labels: Anaphase Interphase S-DNA replication Interphase Prophase G1 – cell grows Mitosis Cytokinesis Metaphase Cell division (M Interphase Telophase Phase) G2 – prepares for mitosis Then on the diagram, lightly color the G1 phase BLUE, the S phase YELLOW, the G2 phase RED, and the stages of mitosis ORANGE. Color the arrows indicating all the interphases in GREEN. Color the part of the arrow indicating mitosis PURPLE and the part of the arrow indicating cytokinesis YELLOW. HUGOT FOR THE DAY!!!! Life is made of cycles. It is up to you to allow completion of each cycle before you move on to the next. If you keep repeating the same mistakes, you stay stuck in your current cycle. Learn, grow, and move forward.