Medical Biology Lab: Cell Cycle PDF

Medical Biology Lab Lab Lab 44 CELL CELL CYCLE CYCLE  CELL REPRODUCTION Cell Division: process by which a cell divides to form two new cells (daughter cells) Three types of cell division, or cell repr...

Medical Biology Lab Lab Lab 44 CELL CELL CYCLE CYCLE  CELL REPRODUCTION Cell Division: process by which a cell divides to form two new cells (daughter cells) Three types of cell division, or cell reproduction – Prokaryotes (bacteria)  divides forming two new identical cells Binary fission – Eukaryotes Mitosis – Cell or organism growth – Replacement or repair of damaged cells Meiosis – formation of sex cells, or gametes Why do cells divide? Cells divide for several reasons Growth: Multicellular organisms grow by increasing the number of cells. As an organism grows, its cells undergo division to produce more cells, allowing the organism to increase in size. Repair and Maintenance: Cell division plays a vital role in replacing damaged, old, or dying cells. This process helps in tissue repair and regeneration, ensuring the proper functioning of organs and tissues in the body. Development: During the development of a multicellular organism, cell division is essential for creating specialized cells that perform specific functions. Cells divide and differentiate to form various tissues, organs, and systems in the body. Reproduction: In unicellular organisms, cell division is the primary means of reproduction. For instance, bacteria reproduce asexually through binary fission, where one cell divides into two identical daughter cells. PROKARYOTIC CELL DIVISION Binary fission – 3 main steps: 1: DNA Replication—DNA is copied, resulting in 2 identical chromosomes 2: Chromosome Segregation—2 chromosomes separate, move towards ends (poles) of cell. 3: Cytokinesis—cytoplasm divides, forming 2 cells – Each new daughter cell is genetically identical to parent cell  THE CELL CYCLE / EUKAYOTIC CELLS G1 phase M phase S phase G2 phase CELL CYCLE-INTERPHASE Interphase: period of growth and DNA replication between cell divisions Three phases: – G1 Phase The G1 phase (Gap 1 phase) is the first stage of the cell cycle where the cell grows, performs its normal functions, and prepares for DNA replication. During G1, the cell increases in size, synthesizes proteins, and accumulates the necessary energy and resources needed for DNA replication in the next phase, S phase. G1 is a critical phase where the cell assesses its environment and internal conditions to ensure it's ready to proceed with the replication of DNA. S Phase The S phase, or Synthesis phase, is the stage in the cell cycle where DNA replication occurs. During this phase, the cell synthesizes a copy of its entire DNA content, ensuring that each daughter cell formed during division receives an identical set of genetic information. This process is fundamental for growth, repair, and the transmission of genetic material to offspring. G2 Phase The G2 phase (Gap 2 phase) is the third stage of the cell cycle. During G2, the cell continues to grow, synthesizes proteins, and prepares for cell division. It's a critical checkpoint where the cell checks for any errors in DNA replication and ensures that the cell is ready for mitosis (M phase) by completing necessary cellular processes and accumulating resources required for division  Chromosomes are structures in cells carrying genes made of DNA. They come in pairs, except in sex cells, and determine an individual's traits. During cell division, they ensure genetic information is passed accurately to new cells. Humans have 46 chromosomes, each holding vital genetic instructions for our characteristics and development. EUKARYOTIC CELL DIVISION Cell cycle continuous process – Cells grow – DNA replicated – Organelles duplicated – Divide to form daughter cells – 2 Main steps: 1: Mitosis (4 steps—Prophase, Metaphase, Anaphase, Telophase) Nucleus divides 2: Cytokinesis—Cytoplasm divide, forming 2 cells Each new daughter cell is genetically identical to parent cell  Mitosis = nuclear division Mitosis is followed by cytokinesis (cell division) The steps of mitosis ensure that each new cell has the exact same number of chromosomes as the original MITOSIS Process that divides cell nucleus to produce two new nuclei each with a complete set of chromosomes Continuous process Four phases (PMAT) – Prophase – Metaphase – Anaphase – Telophase  It has 4 stages 1)Prophase (2)Metaphase (3)Anaphase (4)Telophase.  1.chromosomes visible (sister chromatids) 2. centrioles migrate to the poles (only in animals) 3. nuclear membrane disappears 4. spindle forms 1. chromosomes line up on the equator of the cell spindles attach to centromeres. 1. sister chromatids separate 2. centromeres divide 3. sister chromatids move to opposite poles  1.chromosomes uncoil no chromatin 2. nuclear membranes reform 3. spindle disappears - Occurs at end of Mitosis – --division of the cytoplasm to form 2 new daughter cells --organelles are divided -Daughter cells are genetically identical Cells return to interphase  Checkpoints Throughout the cell cycle, several internal quality control mechanisms or checkpoints represented by biochemical pathways control transition between cell- cycle stages. The cell cycle stops at several checkpoints and can only proceed if certain conditions are met—for example, if the cell has reached a certain size. Checkpoints monitor and modulate the progression of cells through the cell cycle in response to intracellular or environmental signals. Control of the Cell Cycle Regulatory proteins called cyclins control the cell cycle at checkpoints: G1 Checkpoint—decides whether or not cell will divide S Checkpoint—determines if DNA has been properly replicated Mitotic Spindle Checkpoint—ensures chromosomes are aligned at mitotic plate. Cell Cycle Checkpoints CANCER CELLS Result of uncontrolled cell division of cells that have lost ability to regulate cell cycle Reproduce more rapidly than normal cells Masses formed called ‘tumors’  Lesson Summary—Cell Cycle The cell cycle is a repeating series of events, characterizing the life of a eukaryotic cell. Binary fission is a form of cell division in prokaryotic organisms that produces identical offspring. As a eukaryotic cell prepares to divide, the DNA and associated proteins coil into a structure, known as a chromosome. The DNA copies during the S phase of the cell cycle, resulting in a chromosome that consists of two identical chromatids, known as sister chromatids, attached at a region called the centromere. Any cell containing two sets of chromosomes is said to be diploid; the zygote forms from the fusion of two haploid gametes. The cell cycle has five phases: the first growth (G1) phase, the synthesis (S) phase, the second growth (G2) phase, mitosis, and cytokinesis. Mitosis is the division of the nucleus; four distinct phases of mitosis have been recognized: prophase, metaphase, anaphase, and telophase. Cytokinesis is the division of the cytoplasm. The cell cycle is controlled through feedback mechanisms. Cancer results from uncontrolled cell division, due to the loss of regulation of the cell cycle Thank you for listening