In this video, we're going to introduce the cell cycle checkpoints. And so recall from our last lesson video that these cell cycle checkpoints are very important for controlling or regulating the cell cycle, to make sure that errors do not accumulate, and to make sure that the cell does not prematurely enter the next phase of the cell cycle. And so these cell cycle checkpoints really act like stop signs where the cell can pretty much stop and make sure everything is okay before it moves on to the next phase. And so we're going to talk about 4 major checkpoints that control the progress of the cell cycle. And so if we take a look at our image down below, notice we're showing you the image of the cell cycle from our previous lesson videos. But notice here that we've included the 4 major checkpoints, which pretty much act like stop signs throughout the cell cycle, where the cell will literally stop at each of these checkpoints to make sure that everything is okay before it proceeds into the next phase. And so notice that we have these 4 checkpoints here at each of these positions. And so at each of these checkpoints, there are going to be very specific events that occur. And what's really important for you all to note is that the events of these checkpoints really don't need to be memorized. You don't need to memorize them if you understand the cell cycle itself. And so if you understand the events that occur at each phase of the cell cycle, then really you don't need to memorize these checkpoints because the checkpoints and the events that occur at the checkpoints are going to be dictated by the events that occur in the cell cycle. And so the very first checkpoint that we're going to talk about is the G1 checkpoint, which occurs right at the end of the G1 phase of interphase. And so notice that here is the G1 phase of interphase and right at the end of the G1 phase of interphase, there is the G1 checkpoint, which again is going to act like a stop sign for the cell where the cell is going to stop to make sure that everything is okay before it proceeds. And so at the G1 checkpoint, what we need to realize is that the G1 comes just before the S phase and the S phase is where the DNA is going to get replicated or duplicated or synthesized. And so before the DNA gets replicated or duplicated or synthesized, the cell needs to make sure that the DNA doesn't have any errors in it. And if the DNA does have errors in it, then the DNA needs to be fixed before the DNA gets replicated. Otherwise, the DNA, the errors that are in the DNA are just going to get replicated and that won't be something good. And so this G1 checkpoint, again, is going to be dictated by the events of the phases that come after. And so during the G1 checkpoint, again, which acts like a stop sign for the cell, the cell is going to stop and fix any damage or mutated DNA in preparation for DNA replication in the S phase. And so, of course, after the S phase, the DNA is going to get replicated and the centrosome is also going to get replicated. And that leads us to our second checkpoint which comes at the end of the S phase, the S checkpoint. And so if we go up here, we can see that the second checkpoint here is going to be the S checkpoint. And of course during the S checkpoint, what we need to realize is that the cell has just finished replicating or duplicating or synthesizing its DNA. And so what the cell wants to do is it actually wants to confirm the propriety of the DNA to make sure that the DNA was replicated completely and fully and properly. And so, the S checkpoint is going to confirm the proper replication of the genetic material and it's also going to attempt to fix any errors that may have occurred. And so that is what happens at the S checkpoint. Then notice that the 3rd checkpoint after that is the G2 checkpoint which comes at the end of the G2 phase. And what we need to realize about this G2 checkpoint is that the G2 checkpoint comes just before the M phase, mitosis. And so at the G2 checkpoint, the cell pretty much wants to make sure that it has all of the enzymes and proteins that it needs in order for mitosis to proceed properly. And so that's exactly what is going to happen here at the G2 checkpoint. At the G2 checkpoint, the cell again is going to stop because the checkpoints kind of act like stop signs, and the cell is going to stop and ensure that all of the enzymes and proteins that are needed for mitosis and cytokinesis are available. If they are not available, again, the cell is going to stop at this checkpoint to make sure that they are available. And then, of course, last but not least, we have our final checkpoint here which is the M checkpoint which comes right in the middle here at metaphase. And so, of course, during metaphase, we know that all the chromosomes are supposed to line up in the middle and that's exactly what the M checkpoint is checking for. So during the M checkpoint, which really is the metaphase checkpoint, the cell is going to stop and confirm that all of the chromosomes have actually aligned properly at the middle of the cell. And so it's going to check to confirm that all chromosomes are aligned and the spindle fibers are attached properly. And so, again, if any of these checkpoints are not working properly, then that can lead to an unregulated cell cycle, and ultimately, that can lead to the development of cancer. And so these checkpoints are very, very important to make sure that the cell cycle is under control and that it's regulated properly so that cell division occurs only when it's supposed to and that cell division occurs properly. And so this here concludes our introduction to the 4 cell cycle checkpoints, and we'll be able to get some practice applying these concepts as we move forward in our course. So I'll see you all in our next video.
Table of contents
- 1. Introduction to Biology2h 40m
- 2. Chemistry3h 40m
- 3. Water1h 26m
- 4. Biomolecules2h 23m
- 5. Cell Components2h 26m
- 6. The Membrane2h 31m
- 7. Energy and Metabolism2h 0m
- 8. Respiration2h 40m
- 9. Photosynthesis2h 49m
- 10. Cell Signaling59m
- 11. Cell Division2h 47m
- 12. Meiosis2h 0m
- 13. Mendelian Genetics4h 41m
- Introduction to Mendel's Experiments7m
- Genotype vs. Phenotype17m
- Punnett Squares13m
- Mendel's Experiments26m
- Mendel's Laws18m
- Monohybrid Crosses16m
- Test Crosses14m
- Dihybrid Crosses20m
- Punnett Square Probability26m
- Incomplete Dominance vs. Codominance20m
- Epistasis7m
- Non-Mendelian Genetics12m
- Pedigrees6m
- Autosomal Inheritance21m
- Sex-Linked Inheritance43m
- X-Inactivation9m
- 14. DNA Synthesis2h 27m
- 15. Gene Expression3h 20m
- 16. Regulation of Expression3h 31m
- Introduction to Regulation of Gene Expression13m
- Prokaryotic Gene Regulation via Operons27m
- The Lac Operon21m
- Glucose's Impact on Lac Operon25m
- The Trp Operon20m
- Review of the Lac Operon & Trp Operon11m
- Introduction to Eukaryotic Gene Regulation9m
- Eukaryotic Chromatin Modifications16m
- Eukaryotic Transcriptional Control22m
- Eukaryotic Post-Transcriptional Regulation28m
- Eukaryotic Post-Translational Regulation13m
- 17. Viruses37m
- 18. Biotechnology2h 58m
- 19. Genomics17m
- 20. Development1h 5m
- 21. Evolution3h 1m
- 22. Evolution of Populations3h 52m
- 23. Speciation1h 37m
- 24. History of Life on Earth2h 6m
- 25. Phylogeny2h 31m
- 26. Prokaryotes4h 59m
- 27. Protists1h 12m
- 28. Plants1h 22m
- 29. Fungi36m
- 30. Overview of Animals34m
- 31. Invertebrates1h 2m
- 32. Vertebrates50m
- 33. Plant Anatomy1h 3m
- 34. Vascular Plant Transport2m
- 35. Soil37m
- 36. Plant Reproduction47m
- 37. Plant Sensation and Response1h 9m
- 38. Animal Form and Function1h 19m
- 39. Digestive System10m
- 40. Circulatory System1h 57m
- 41. Immune System1h 12m
- 42. Osmoregulation and Excretion50m
- 43. Endocrine System4m
- 44. Animal Reproduction2m
- 45. Nervous System55m
- 46. Sensory Systems46m
- 47. Muscle Systems23m
- 48. Ecology3h 11m
- Introduction to Ecology20m
- Biogeography14m
- Earth's Climate Patterns50m
- Introduction to Terrestrial Biomes10m
- Terrestrial Biomes: Near Equator13m
- Terrestrial Biomes: Temperate Regions10m
- Terrestrial Biomes: Northern Regions15m
- Introduction to Aquatic Biomes27m
- Freshwater Aquatic Biomes14m
- Marine Aquatic Biomes13m
- 49. Animal Behavior28m
- 50. Population Ecology3h 41m
- Introduction to Population Ecology28m
- Population Sampling Methods23m
- Life History12m
- Population Demography17m
- Factors Limiting Population Growth14m
- Introduction to Population Growth Models22m
- Linear Population Growth6m
- Exponential Population Growth29m
- Logistic Population Growth32m
- r/K Selection10m
- The Human Population22m
- 51. Community Ecology2h 46m
- Introduction to Community Ecology2m
- Introduction to Community Interactions9m
- Community Interactions: Competition (-/-)38m
- Community Interactions: Exploitation (+/-)23m
- Community Interactions: Mutualism (+/+) & Commensalism (+/0)9m
- Community Structure35m
- Community Dynamics26m
- Geographic Impact on Communities21m
- 52. Ecosystems2h 36m
- 53. Conservation Biology24m
11. Cell Division
Cell Cycle Regulation
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