Chapter 12: The Cell Cycle Flashcards
What is mitosis?
a type of cell division that occurs in eukaryotic cells, leading to the production of two daughter cells that are genetically identical to the parent cell.
What are the three reasons that cells divide?
- Reproduction
- Growth and development
- Tissue Renewal
Describe the structural organization of a prokaryotic genome vs a eukaryotic genome.
Prokaryotic Genome:
- Single circular chromosome located in the nucleoid region, not enclosed by a membrane
- Contain plasmids (small, circular DNA molecules that can replicate independently of the chromosome.)
Eukaryotic Genome:
- Larger, multiple linear chromosomes
- Humans have 46 chromosomes (23 pairs)
- Chromosomes located in the nucleus, seperated by a membrane
What are sister chromatids.
The duplicate identical copies that the parent chromosome makes of their chromosomes.
Describe the Kenetichore, and the difference between two spindle fibers: kinetochore microtubules and nonkinetochore microtubules.
Kinetochore Protein Complex: protein complex known as the Kinetochore that serves as the attachment site for microtubules during cell division.
Kinetochore Microtubules: Microtubules that directly attach to the kinetochore protein complex at the centromere of chromosomes.
Nonkinetochore Microtubules: Microtubules that do not directly attach to kinetochore protein complex, but instead extend from the centrosomes.
Name and describe the phases of interphase in the cell cycle.
G1 (Gap 1): The cell performs its normal functions, grows and synthesizes proteins necessary for DNA replication and cell division.
S (Synthesis) Phase: DNA replication occurs, synthesizing an identical copy of each chromosome.
G2 (Gap 2): The cell continues to grow and prepares for cell division by creating proteins and organelles that are necessary for mitosis and meiosis.
Name and describe the five steps of the Mitotic Phase.
- Phrophase: Chromosomes condense and are now visible, the nuclear envelope breaks down, and the centrosomes move to opposite poles of the cell forming spindle fibers.
- Prometaphase: The nuclear envelope is completely broken down. Spindle fibers interact with the chromosomes and attach to the kinetochores of the chromosomes, which begin to move toward the center of the cell.
- Metaphase: Chromosomes align at the metaphase plate, attached to spindle fibers originating from opposite poles of the cell.
- Anaphase: The sister chromatids of each chromosome are pulled apart toward opposite poles of the cell by the shortening of the spindle fibers.
- Telophase/Cytokinesis: Chromosomes arrive at opposite poles and chromatin decondenses. Cytoplasm seperates and the nuclear envelope reforms around the two new cells.
What is cytokinesis? Compare cytokinesis in animals vs plants.
It is the seperation of cytoplasms. cytokinesis formation of a cleavage furrow in animal cells or the construction of a cell plate in plant cells.
Cleavage furrow: a shallow groove that appears on the cell surface near the equator of the cell during cytokinesis. As the cleavage furrow deepens, it eventually pinches the cell in two, leading to the completion of cell division.
Cell plate: a flattened, disk-shaped structure made of vesicles derived from the golgi apparatus, that fuses with the plasma membrane, dividing the cytoplasm of the parent cell into two daughter cells
What is the metaphase plate?
A hypothetical plane or region that forms during metaphase of mitosis or meiosis located at the center of the cell, midway between the two poles of the mitotic spindle. During metaphase, the chromosomes line up along the metaphase plate, becoming fully condensed and attached to the spindle fibers via their kinetochores.
List some internal signals in which cells divide in response to.
-Cell cycle Checkpoints: Various checkpoints within the cell cycle monitor key events to ensure that the cell is ready to proceed to the next stage of the cycle.
- Cyclins and cyclin-dependent reactions: Proteins that regulate the progression of the cell cycle by forming complexes that activate or deactivate specific proteins involved in cell division
List some external signals in which cells divide in response to.
Growth factors: signaling molecules that are released by either neighboring cells or the ECM that stimulate cell division by binding to receptors on the cell surface and activating intracellular signaling pathways.
Major growth rules include cell-to-cell contact inhibition (normal cells typically stop dividing when they come into contact with neighboring cells) and ancchorage dependence (many cells require attachment to a solid surface (anchorage) to divide
What happens if the two major growth rules of normal cells aren’t followed?
Instead of forming a monolayer and stopping production, cells begin piling up on each other, forming cancer. this is because cancer can make its own growth factor, convey fake growth factor signals, and may have an abnormal cell cycle control system.
Define cyclin and cyclin dependent kinases.
cyclin-dependent kinases (CDKs) and cyclins are protein complexes that drive the progression of the cell cycle. When cyclin binds to a CDK, it activates the CDK, allowing it to perform its specific function in the cell cycle.
Levels of cyclins fluctuate, with their concentrations increasing and decreasing at specific points in the cell cycle.
After fulfilling its role in activating CDKs and driving specific phases of the cell cycle, cyclin is targeted for degradation. Degradation of cyclin is essential for the cell to exit from a particular phase of the cell cycle
What is MPF?
Maturation-Promoting Factor is a complex of cyclin and cyclin-dependent kinase that promotes the transition from G2 phase to M phase by phosphorylating target proteins involved in mitotic processes.
Explain how the abnormal cell division of cancerous cells escapes normal cell cycle controls.
Via mutations that disrupts the regulation of cell division such as:
Checkpoint Dysfunction: Mutations can disable the cell cycle checkpoints that normally ensure proper DNA replication, repair damaged DNA, and prevent the progression of damaged cells into mitosis.
Dysregulated Cyclin-CDK Complexes: Overexpression of cyclins or mutations in CDKs can disrupt the balance between proliferation and inhibition.
Tumor Suppressor Gene Inactivation: Mutations that inactivate tumor suppressor genes, such as p53 and Rb, that normally inhibit cell cycle progression or trigger apoptosis in response to DNA damage or other abnormalities, to allow cancer cells to evade these.
Oncogene Activation: Mutated normal genes that promote cell proliferation when active. Oncogene activation can stimulate cell cycle progression even in the absence of normal growth signals.
