Cell Cycle and Cell Division PDF

8/27/24, 8:24 PM Platform | Study Fetch The Cell Cycle and Cell Division (00:00:34 - 00:00:46)The Cell Cycle and Terminology The genome is the complete set of DNA in the cell, including the code for all proteins and regulatory r...

8/27/24, 8:24 PM Platform | Study Fetch The Cell Cycle and Cell Division (00:00:34 - 00:00:46)The Cell Cycle and Terminology The genome is the complete set of DNA in the cell, including the code for all proteins and regulatory regions. Homologous chromosomes are the paired chromosomes, one from each parent, that have many similarities but also some differences. Sister chromatids are the copies of a replicated chromosome joined at the centromere. Kinetochores are proteins that act as structural anchors at the centromere. (00:01:15 - 00:01:30)Karyokinesis vs. Cytokinesis Karyokinesis is the division of the nucleus. Cytokinesis is the division of the cell membrane, the actual pinching off of the cell. (00:01:30 - 00:01:58)Stages of the Cell Cycle G1 (Growth 1) is the growth phase where the cell produces more cytoplasm, proteins, and organelles. G0 is a non-dividing, post-mitotic state, like in neurons in the brain. S (Synthesis) is the phase where the cell replicates its DNA. G2 (Growth 2) is the phase where the cell does additional growth and proofreading to ensure S phase went correctly. (00:00:23 - 00:00:34)Overview of Cell Division 1. We will discuss the cell cycle and terminology. 2. Then we will cover mitosis. 3. Finally, we will discuss meiosis. (00:00:13 - 00:00:23)Introduction to Cell Division There are two main types of cell division: mitosis and meiosis. These will be the focus of our lesson today. The Cell Cycle and Mitosis (00:02:47 - 00:03:01) The cell cycle consists of several phases: G1, S, G2, and M phase (mitosis). A mnemonic to remember the cell cycle is "Go Sam, go make cake." G1 phase is the first growth phase. S phase is the synthesis phase where DNA is replicated. G2 phase is the second growth phase. M phase is mitosis, where the cell divides. Cytokinesis is the final stage where the cell physically separates. Microtubule Organizing Centers(00:03:01 - 00:03:25) Kinetochore microtubules attach the chromosomes to the kinetochore. The microtubule organizing center (MTOC) is the source of the microtubules that anchor the chromosomes and help them split apart. Spindle Formation and Tension(00:03:25 - 00:03:41) The spindle formation creates tension as the chromosomes polarize and separate. Astral microtubules provide anchor points by pulling the MTOCs towards opposite sides of the cell. https://www.studyfetch.com/platform/studyset/66cd116dd279f5220d947c66/material/66ce6bd854668773b0c61dfd/document?go=note 1/5 8/27/24, 8:24 PM Platform | Study Fetch Microtubule Interactions(00:03:41 - 00:04:00) Polar microtubules arise from the MTOC and interweave, pushing against each other to help push the cells apart. Centrosomes and Centrioles(00:04:00 - 00:04:25) The centrosome is the MTOC of the cell. The centrosome contains two centrioles oriented perpendicularly. The centrioles have a structure of 99 triplets (or 27) of microtubules. Mitosis: Prophase(00:04:51 - 00:05:14) In prophase: Chromosomes condense and become visible. The spindle fiber begins to form from the centrosome. The nuclear envelope breaks down. The nuclear lamins start to dissociate. The centrosomes move towards opposite poles. Mitosis: Prometaphase(00:05:14 - 00:05:28) In prometaphase, the chromosomes... The Mitotic Spindle and Cell Division Mitotic Spindle Formation (00:05:28 - 00:05:45) The mitotic spindle is going to form at this point Chromosomes will line up at the metaphase plate Each sister chromatid will be attached to a spindle fiber on either side of the cell Anaphase (00:05:45 - 00:06:02) Segregation is ready to start moving on to anaphase The centromeres will split and the sister chromatids, now individual chromosomes, will be pulled apart and dragged towards opposite ends of the cell The spindle fibers will be working hard, pushing against each other and pulling, to separate the chromosomes Telophase (00:06:19 - 00:06:33) The chromosomes will arrive at opposite poles and start to de-condense Nuclear envelopes will start to form around the separate nuclei The mitotic spindle will break down https://www.studyfetch.com/platform/studyset/66cd116dd279f5220d947c66/material/66ce6bd854668773b0c61dfd/document?go=note 2/5 8/27/24, 8:24 PM Platform | Study Fetch Cytokinesis (00:06:33 - 00:06:59) The mitotic spindle must be disassembled for the cell to divide Certain chemotherapy drugs can prevent spindle breakdown, freezing the cell and causing it to die In plant cells, a new cell wall will form to separate the two daughter cells Cell Cycle Regulation (00:06:59 - 00:07:30) The cell cycle is regulated by cyclins and cyclin-dependent kinases (CDKs) There are different cyclins for each phase of the cell cycle The cyclins spike and drop during each phase, signaling the cell to progress to the next phase Cell Size Limitations (00:07:30 - 00:08:00) As cells grow, the increasing volume compared to surface area inhibits the diffusion of nutrients and gases This is why there are no single-celled organisms the size of humans - multicellular organisms are necessary to overcome this limitation Cell Division and Meiosis Metabolic Demands and Cell Division (00:08:00 - 00:08:32) As a cell increases in size, the surface area to volume ratio decreases This can lead to issues with diffusion of gases and nutrients into the cytoplasm There is an optimal surface area to volume ratio that meets the metabolic demands of the cell If the cell gets too large, it signals the cell to divide in order to maintain this optimal ratio Transcripts and Protein Production (00:08:32 - 00:09:00) As a cell grows larger, it needs to produce more transcripts and proteins to meet its metabolic demands The genome can only produce transcripts at a certain rate In order to produce enough transcripts and proteins, the cell will need to duplicate its genome Cell Cycle Regulation (00:09:00 - 00:09:15) https://www.studyfetch.com/platform/studyset/66cd116dd279f5220d947c66/material/66ce6bd854668773b0c61dfd/document?go=note 3/5 8/27/24, 8:24 PM Platform | Study Fetch Cyclin-dependent kinases (CDKs) will phosphorylate substrates and complex with cyclins to activate the cell cycle These CDK-cyclin complexes drive the progression of the cell cycle Meiosis Overview (00:09:15 - 00:10:04) Meiosis produces 4 haploid daughter cells from a single diploid parent cell The process involves: Homologous chromosomes pairing and undergoing crossing over Separation of homologous chromosomes into haploid daughter cells Further division of the haploid cells into single haploid cells Meiosis I (00:10:04 - 00:10:30) Meiosis I starts with a single diploid parent cell The chromosomes condense and the nuclear envelope breaks down Crossing over occurs between homologous chromosomes during prophase I In metaphase I, the pairs of homologous chromosomes move to the center of the cell In anaphase I, the homologous chromosomes separate and move to opposite poles of the cell Meiosis II (00:10:30 - 00:10:41) After meiosis I, the cell undergoes a second round of cell division (meiosis II) In meiosis II: The chromosomes align at the metaphase plate The sister chromatids then separate and move to opposite poles of the cell Meiosis: The Cellular Dance of Genetic Diversity (00:10:41 - 00:10:58) The chromosomes gather in the cell The cytoplasm divides This produces two haploid daughter cells (00:10:58 - 00:11:11) The two haploid daughter cells undergo meiosis II This produces four haploid daughter cells These four cells are the germ cells of the organism https://www.studyfetch.com/platform/studyset/66cd116dd279f5220d947c66/material/66ce6bd854668773b0c61dfd/document?go=note 4/5 8/27/24, 8:24 PM Platform | Study Fetch (00:11:11 - 00:11:28)Stages of Meiosis II: Prophase II: A new spindle forms around the chromosomes Metaphase II: Chromosomes line up at the equator Centromeres divide and chromatids move to opposite poles (00:11:28 - 00:11:41) A nuclear envelope forms around each set of chromosomes The cytoplasm divides This produces the sperm or egg cells (germ cells) for reproduction (00:11:41 - 00:11:54) This is an important process to understand Highlights key characteristics of human cells (00:11:54 - 00:12:10)Key Differences Between Meiosis and Mitosis: Parent cell has 46 chromosomes before division Meiosis duplicates to 92 chromosomes, mitosis does not Meiosis involves crossing over, mitosis does not (00:12:10 - 00:12:25) Crossing over in meiosis generates new gene combinations This creates genetic diversity, so offspring are not identical to parents (00:12:25 - 00:12:46) Meiosis I produces two haploid daughter cells Mitosis produces diploid daughter cells Meiosis II then produces four haploid germ cells (00:12:46 - 00:12:57) Meiosis II produces the final four haploid germ cells These will be the sperm or egg cells for the organism (00:12:57 - 00:13:07) There are many numbers and stages to keep track of Be sure to understand the transitions from diploid to haploid (00:13:07 - 00:13:18) Know how many copies of chromosomes are in each cell Understand when the ploidy (diploid vs haploid) changes (00:13:18 - 00:13:27) Mastering cell division and meiosis is crucial You'll be able to answer exam questions confidently https://www.studyfetch.com/platform/studyset/66cd116dd279f5220d947c66/material/66ce6bd854668773b0c61dfd/document?go=note 5/5