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Ap Bio Mod 24-25
| Question | Answer |
|---|---|
| How do Bacteria and other prokaryotes divide? | through binary fission -resulting in two indentical bacterial daughter |
| What two organelles in eukaryotic cells divide by binary division | mitochondria and chloroplasts |
| Chromosomes | tightly packed structures of DNA and proteins that carry genes and store genetic information in a cell. |
| Prokaryotic vs. Eukaryotic Cell Division | Prokaryotic: divide by binary fission—the single circular Dna is copied, and the cell splits into two cells. -No nucleus or mitotic stages. Eukaryotic: divide by mitosis linear chromosomes are split through miotic stages -nucleus involved |
| M phase | the stage of the cell cycle when the cell divides, including mitosis (nuclear division) and cytokinesis (division of the cytoplasm). |
| Interphase: | the part of the cell cycle when the cell grows, carries out normal functions, and replicates its DNA in preparation for division. -made up of 3 subphases (G1, G2, and S phase) |
| Chromosomes | -dna molecules that are surrounded by association proteins |
| Why does a cell undergo cell divison | -to grow and develop -to heal injuries |
| G1 phase | Cell grows, and produces proteins and organelles needed for DNA replication. |
| S phase (Synthesis | DNA is replicated, producing sister chromatids for each chromosome. |
| G2 phase | Cell continues growth, checks replicated DNA, and prepares proteins and structures needed for cell division. |
| G0 phase | A resting or non-dividing state where cells exit the cell cycle and perform specialized functions (may be temporary or permanent). |
| Sister chromatids | identical copies of the same single stranded chromosome that are held together by a centromere - |
| Centromeres | the region on chromosomes that acts as a point of attachment for sister chromosomes to keep them together |
| Chromatin | The uncondensed DNA that makes up chromosomes, typically found in a loosely packed form during interphase. -they condense into chromosomes when they enter mitosis and meiosis |
| mitotic spindles | a bundle of fibers made of microtubules which help move chromosomes during mitosis -made by centrosomes |
| Kinetochore | A protein structure that forms on the centromere of each chromatid, serving as the attachment site for spindle fibers during cell division. |
| Prophase | -nuclear envelope breaks down -chromosomes condense -mitotic spindles form -Spindle attachment to kinetochores |
| Metaphase | -mitotic spindles pull chromosomes to center of the cell |
| Anaphase | -mitotic spindles separate sister chromosomes. by pulling them to opposite poles of the cell |
| Telophase | The stage of cell division in which chromosomes arrive at opposite poles, begin to decondense into chromatin, the nuclear envelope reforms, and the spindle apparatus breaks down. |
| Cytokinesis | The process that divides the cytoplasm, physically separating the cell into distinct daughter cells (via a cleavage furrow in animals or a cell plate in plants). |
| Contractile ring: | A ring of actin and myosin filaments that forms beneath the cell membrane during cytokinesis in animal cells, tightening to create a cleavage furrow that pinches the cell into two daughter cells. |
| cancer | uncontrolled and rapid cell growth |
| Cyclin-depdent kinases (CDKs) | - kinases that are activated by cyclins -they allow cell cycle to. progress when they bind to cyclin - |
| How do Cyclin-depdent kinases (CDKs) allow the cell cycle to progress? | by phosphorylating key target proteins that trigger the events of each cell-cycle stage. -CDKs add phosphate groups to proteins that: Push the cell past checkpoints (G1, G2, M) Initiate DNA replication Promote mitosis and chromosome separation |
| Cyclins | Proteins whose levels fluctuate during the cell cycle. Concentration rises and falls at specific phases to activate CDKs. |
| What are the 3 cell cycle checkpoints | -DNA damage checkpoint -DNA replication checkpoint -Spindle assembly checkpoint |
| DNA Damage Checkpoint (Checkpoint between G1 & S) | When: End of G1 phase before S phase What is checked: Whether DNA is damaged before replication Action: If damage is detected, cell cycle is paused for repair or apoptosis may be triggered |
| DNA Replication Checkpoint (Checkpoint between G2& M) | When: End of G2 phase before M phase What is checked: Whether all DNA has been accurately replicated Action: Prevents entry into mitosis until replication is complete |
| Spindle Assembly Checkpoint (Checkpoint between Metaphase and Anaphase ) | When: End of Metaphase before Anaphase What is checked: Whether all chromosomes are properly attached to the spindle and aligned at the metaphase plate Action: Delays anaphase until all chromosomes are correctly attached to prevent poor separation |
| What environmental factors damage DNA? | radiation and chemicals |
| Apoptosis | Programmed cell death that is triggered if cell damage is irreparable -prevents the damaged cells from replicating to increase |
| P53 | -A tumor suppressor protein that is regulator of the cell cycle. -If damage is irreparable, p53 can trigger apoptosis -Known as the "guardian of the genome" because it prevents mutations and cancer development. |
| Describe how mutations in p53 leads to cancer | Mutated p53 cannot stop the cell cycle or trigger apoptosis in response to DNA damage. - Thus, cells with damaged DNA continue dividing, accumulating mutations. -Thus every new cell generation becomes more resistance to p53, and divides uncontrollably |
| Proto-oncogenes: | Normal genes that encode proteins promoting cell growth and division -They encode proteins like growth factors, cyclins, and CDKs that stimulate cell division. |
| Oncogenes: | Mutated or overactive proto-oncogenes that cause uncontrolled cell division, contributing to cancer development. |
| RB (Retinoblastoma protein): | A tumor suppressor protein that regulates the G1/S checkpoint of the cell cycle. -Function: Binds and inhibits E2F transcription factors, preventing progression into S phase until the cell is ready. |
| Contact (or Positional) Inhibition: | Cells stop dividing when they touch neighboring cells, preventing overcrowding in tissues. |
| Anchorage Dependence: | Cells must be attached to a solid surface or extracellular matrix to divide; |
| Density-Dependent Inhibition: | Cells stop dividing once the culture reaches a certain density, ensuring proper tissue size |
Created by:
KenechukwuIE