Booster Cheat Sheets - Cell Division (PDF)

© Copyright 2024, Booster Prep Inc. Booster Prep Booster Cheat Sheets – Cell Division (1/2) All Rights Res er...

© Copyright 2024, Booster Prep Inc. Booster Prep Booster Cheat Sheets – Cell Division (1/2) All Rights Res erved. Introduction to Cell Division Cell Division The Cell Cycle Regulation of Cell Cycles The Spindle Apparatus Cell division is nuclear division (karyokinesis) followed by The cell cycle is divided into interphase (G1, S, and G2 ) and the Surface to Volume Ratio The spindle apparatus forms during cytoplasmic division (cytokinesis) Mitotic phase (mitosis and cytokinesis) prophase When Surface area to In diploid cells, there are two copies of every Interphase begins after mitosis and cytokinesis are complete Volume ratio (S/V) is small Microtubules and the mitotic chromosome, forming pairs called homologous (when the cells are replicated and physically separated). It (E.g., when the cell becomes spindle is crucial to cell division chromosomes consists of a G1, S, and G2 phase. too large), cellular exchange during the mitotic phase is hard, and leads to cell E.g., Anti-tumor drugs acting as Humans have 46 chromosomes (23 homologous pairs) G1: Cell increases in size and G1 checkpoint ensures death or cell division to microtubule inhibitors in cancers: Animal cells have cellular structures called everything is ready for DNA synthesis (cells produce protein, increase surface area. This is the drugs stabilize microtubules, centrosomes. Each centrosome contains a pair of ribosomes, and mitochondria, replicates organelles). Most why cells are limited in how preventing chromosome and centrioles cell growth in volume occurs here. large they can grow. chromatid separation and causing cell cycle arrest (no cell division) Centrioles produce the spindle fibers that will separate S: DNA synthesis: second molecule of DNA replicated from Genome to Volume Ratio E.g., a virus impacting the mitotic sister chromatids during anaphase the first, creating sister chromatids. Note that it is during spindle most affects a cell during centrosome As Genome to Volume ratio microtubule the S phase when DNA is replicated – not during mitosis! the mitotic phase triplet (G/V) decreases, the cell G2: Rapid cell growth continues to occur. Preparation of exceeds the ability of its Each sister chromatid has a genetic material for cellular division. Some organelles replicate. genome to produce proteins kinetochore to which microtubules G0: Inactive state of cells not actively growing or dividing needed to regulate the cell. attach – microtubules do not attach centriole (e.g., nerve cells and cardiac cells) to the chromosomes directly centriole Mitosis Prophase (46 chromosomes, 92 chromatids) Metaphase (46 chromosomes, 92 chromatids) Anaphase (92 chromosomes, 92 chromatids) Telophase and cytokinesis (92 chromosomes, 92 chromatids) Nucleus disassembles, nucleolus disappears. Chromosomes line up. Each metaphase Microtubules shorten and each chromosome is pulled apart into two separate Nuclear envelope re-forms. Chromosomes decondense back Chromatin condenses into chromosomes. chromosome consists of 2 attached sister chromatids (once physically separated, each chromatid is considered a into chromatin and nucleoli reappear. After cytokinesis, there chromatids. Each chromatid is complete with chromosome, so the chromosome number has doubled). Chromosomes pulled to are 46 chromosomes and 46 chromatids in each cell. Early mitotic Condensing a centromere and attached kinetochore. opposite poles (disjunction). At the end of this phase, each pole has a complete set spindle chromosomes of chromosomes. Metaphase Chromatin Nuclear envelope Intact nuclear plate Daughter envelope Mitotic spindle chromosomes Nuclear envelope fragments Chromosomes line up at the center  © Copyright 2024, Booster Prep Inc. Booster Prep Booster Cheat Sheets – Cell Division (2/2) All Rights Res erved. Meiosis Sources of Genetic Variation Meiosis produces four, non-identical haploid daughter cells from one diploid parent cell. It does this by repeating nuclear division twice. Genetic recombination during meiosis and sexual reproduction originates from three events: Meiosis can be divided into meiosis I (homologous chromosomes separate) and meiosis II (sister chromatids separate). 1. Crossing over (non-sister chromatids of two homologous chromosomes exchanging genetic Meiosis I material) occurs during prophase I sister 2. During metaphase I, the random orientation of homologous chromosomes allows for the Prophase I (46 chromosomes, 92 chromatids) chromatids Prophase I 2n production of gametes with many different assortments of alleles (independent assortment) Spindles form, nuclear envelope breaks down Chromosomes pair up lengthwise through a process called synapsis, TETRAD 3. Random joining of gametes (which sperm fertilizes which egg) forming tetrads which need to form for crossing over to occur. Pairs are physically linked through chiasmata, regions where crossover occurs Crossing Over Independent Assortment Random Joining of Gametes Metaphase I During Prophase I Microtubules attach to chromosomes at kinetochores and move Synapse Cros sing Over them towards the metaphase plate homologous Metaphase I (46 chromosomes, 92 chromatids) chromosomes synaptonemal + = Homologous chromosomes are arranged at the metaphase plate complex Anaphase I Independent assortment of chromosomes occurs because the arrangement of homologous chromosomes is random Independent Assortment + = Anaphase I (46 chromosomes, 92 chromatids) Homologous chromosomes separate and spindle apparatus guides the Telophase I chromosomes to opposite poles Telophase I and cytokinesis (46 chromosomes, 92 chromatids) + = Homologous chromosomes are separated from each other to each end of the Gametes Outcome 1 Gametes Outcome 2 cell. Cytokinesis then results in two haploid daughter cells (each containing Prophase II one chromosome from every homologous pair) Pro-Tip: Genes closer together on a chromosome are more likely to be inherited together, which is called genetic linkage. Genes that are physically closer together are less likely to be separated Meiosis II during crossing over. Prophase II (23 chromosomes, 46 chromatids) Metaphase II Comparing Meiosis and Mitosis Spindle apparatus forms and microtubules move chromosomes towards metaphase plate Meiosis Mitosis Metaphase II (23 chromosomes, 46 chromatids) Chromosome number Reduced by half Remains the same Sister chromatids are no longer genetically identical due to crossing over Anaphase II Chromosomes lined up at metaphase plate Number daughter cells produced 4 haploid (1n) cells 2 diploid (2n) cells Anaphase II (46 chromosomes, 46 chromatids) E.g., spermatozoa as an end Chromatids separate, moving towards opposite ends product of spermatogenesis Separated chromatids are now chromosomes Telophase II Genetically Different Identical Telophase II and cytokinesis (46 chromosomes, 46 chromatids) Rounds of cell division 2 1 Nuclei formation and decondensing of chromosomes Results in four genetically distinct daughter cells in total Division of genetic information Sister chromatids separate at Sister chromatids separate anaphase II, homologous during anaphase 23 chromosomes, 23 chromatids (1n) per cell chromosomes separate at n n n n anaphase I