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The-Cell-Cycle mitosis and meiosis .pptx
- 1. The Cell Cycle MolecularInsights into Cell Division and Genome Regulation Presented by: Group 1 (1 to 16) BIOCHEMISTRY
- 2. Introduction to theCell Cycle The cell cycle is a vital process. It ensures accurate DNA replication. Cells grow, duplicate DNA, and divide. This precise sequence safeguards genetic material. Every cell division demands DNA integrity.
- 3. Phases of theCell Cycle 1 G1 Phase Cell grows. Proteins synthesize. DNA is relaxed, unreplicated. 2 S Phase DNA replication occurs. Chromosomes duplicate. Sister chromatids form. 3 G2 Phase Further cell growth. DNA checked for errors. Prepares for division. 4 M Phase Mitosis: Chromosomes segregate. Nuclei divide. 5 Cytokinesis Physical cell division. Two new cells form.
- 4. DNA Replication inS Phase DNA replication begins at origins. It proceeds bidirectionally. DNA polymerases synthesize new strands. This ensures identical genomes. Helicase unwinds DNA. SSBs stabilize it. Ligase rejoins fragments. Proofreading corrects errors. Mismatch repair provides fidelity.
- 5. Mitosis – Distributionof DNA Prophase Chromatin condenses. Chromosomes become visible. Spindle fibers begin forming. Metaphase Chromosomes align centrally. They attach to spindle fibers. Anaphase Sister chromatids separate. They move to opposite poles. Telophase Nuclear envelopes reform. Chromosomes de-condense. Spindle disappears. Cytokinesis Cytoplasm divides. Two identical daughter cells form.
- 6. Meiosis – Formationof Gametes Meiosis is a specialized cell division process essential for sexual reproduction. It reduces the chromosome number by half, producing gametes such as sperm and egg cells. This process occurs in two main stages: Meiosis I and Meiosis II. This reduction is crucial for maintaining a constant chromosome number across generations after fertilization, ensuring vital genetic diversity.
- 7. Meiosis I: ReductionalDivision 1. Prophase I: The longest and most complex phase. Chromatin condenses, homologous chromosomes pair up to form bivalents (synapsis), and crossing-over occurs, exchanging genetic material between non-sister chromatids. This genetic recombination is a primary source of genetic variation. 2. Metaphase I: Homologous pairs align randomly along the metaphase plate, ready for separation. Independent assortment of these pairs contributes significantly to genetic diversity. 3. Anaphase I: Homologous chromosomes separate and move to opposite poles of the cell. Sister chromatids remain attached. 4. Telophase I & Cytokinesis I: Chromosomes decondense, nuclear envelopes may reform, and the cytoplasm divides, resulting in two haploid cells, each with replicated chromosomes (sister chromatids).
- 8. Meiosis II: EquationalDivision Meiosis II is very similar to mitosis but starts with haploid cells. No further DNA replication occurs before Meiosis II. 1. Prophase II: Chromosomes condense again, and spindle fibers form in each of the two haploid cells. 2. Metaphase II: Sister chromatids align along the metaphase plate in each cell. 3. Anaphase II: Sister chromatids finally separate and move to opposite poles, becoming individual chromosomes. 4. Telophase II & Cytokinesis II: Nuclear envelopes reform around the separated chromosomes, and the cytoplasm divides in each cell. This results in a total of four genetically unique haploid gametes from the original diploid cell.
- 9. Regulation of theCell Cycle Cyclins Regulate CDK activity. Their levels fluctuate. CDKs Cyclin-dependent kinases. Phosphorylate proteins. Drive cell progression. 2 Checkpoints Ensure cell readiness. Prevent errors. Safeguard DNA integrity. Dysregulation Loss of control. Leads to cancer. Uncontrolled proliferation.
- 10. Clinical Relevance –Cancer and Therapeutics Uncontrolled cell growth leads to tumors. Mutations in p53, RB, BRCA1/2 disrupt control. Chemotherapy targets dividing cells. Doxorubicin and paclitaxel are common agents. Novel therapies inhibit CDKs. Checkpoint regulators are promising. Future treatments focus on precision.
- 11. Conclusion Regulated Process Cell cycleis tightly controlled. Linked to DNA synthesis. Essential for segregation. Profound Implications Understanding its regulation is key. Impacts developmental biology. Crucial for genetics. Cancer Treatment Insights drive new therapies. Targeted approaches emerge. Hope for future cures.