Cell Cycle and Cell Division PDF

CELL CYCLE Cell Division Cell Cycle is a cycle of stages that cells pass through to allow them to divide and produce new cells. basic function: is to duplicate accurately the vast amount of DNA in the chromosomes and then segregate the copies precisely into two genetically identical daug...

CELL CYCLE Cell Division Cell Cycle is a cycle of stages that cells pass through to allow them to divide and produce new cells. basic function: is to duplicate accurately the vast amount of DNA in the chromosomes and then segregate the copies precisely into two genetically identical daughter cells. Cell Cycle  Phases of Cell Cycle G1 Phase the newly formed daughter cell grows there are flurries of protein and organelle production as well as literal increase in the size of the cell.  Phases of Cell Cycle S Phase synthesis of new chromosomes from raw materials cell focuses on replicating its entire genome  Phases of Cell Cycle G2 Phase characterized by lots of protein production. many cells check to make sure that both copies of their DNA are correct and intact  Phases of Cell Cycle Mitosis the “parent” cell goes through a complex series of steps to ensure that each “daughter” cell will get the materials it needs to survive, including a copy of each chromosome.  Phases of Cell Cycle G0 Phase a metabolic state meant only to maintain the daughter cell, not prepare for cell division.  Cell Cycle Checkpoints A checkpoint is one of several points in the eukaryotic cell cycle at which the progression of a cell to the next stage in the cycle can be halted until conditions are favorable (e.g. the DNA is repaired). These checkpoints occur near the end of G1, at the G2/M transition, and during metaphase Cell Division the division of a cell into two daughter cells with the same genetic material. types: Prokaryotic Cell Division (Binary Fission) Eukaryotic Cell Division (Mitosis) Ekaryotic Cell Division (Meiosis) Prokaryotic Cell Division (Binary Fission) "division in half" asexual reproduction by a separation of the body into two new bodies. an organism duplicates its genetic material, or deoxyribonucleic acid (DNA), and then divides into two parts (cytokinesis), with each new organism receiving one copy of DNA. Prokaryotic Cell Division (Binary Fission)  Eukaryotic Cell Division (Mitosis) is a form of eukaryotic cell division that produces two daughter cells with the same genetic component as the parent cell. the “goal” of mitosis is to make sure that each daughter cell gets a perfect, full set of chromosomes Pee on the MAT (nmemonics) Stages of Mitosis Pee on the MAT Prophase Metaphase Anaphase Telophase Eukaryotic Cell Division (Meiosis) is a process where a single cell divides twice to produce four cells containing half the original amount of genetic information. Its "goal" is to make daughter cells with exactly half as many chromosomes as the starting cell has two-step division process: Meiosis I and Meiosis II Meiosis I Homologue pairs separate Stages: Prophase I Metaphase I Anaphase I Telophase I Meiosis I  Prophase I As in mitosis, the chromosomes begin Meiosis I to condense, but in meiosis I, they also pair up. Each chromosome carefully aligns with its homologue partner so that the two match up at corresponding positions along their full length. nuclear envelope breaks up and disappears. nucleolus also vanishes spindle apparatus begins to extend outward from the two centrosomes, which move to the opposite ends ("poles") of the cell  Metaphase I each pair of bivalents (two chromosomes, four Meiosis I chromatids total) align on the metaphase plate. the position of each chromosome in the bivalents is random - either parental homolog can appear on each side.  Anaphase I Meiosis I homologous chromosomes separate. homologous chromosomes, each containing two chromatids, move to separate poles unlike in mitosis, the centromeres do not split and sister chromatids remain paired  Telophase I & Cytokinesis Meiosis I the homologs of each bivalent arrive at opposite poles of the cell a new nuclear membrane forms around each set of chromosomes cytokinesis then divides the cell into two daughter cells. Each of the two daughter cells is now haploid (n), with half the number of chromosomes per nucleus as in meiosis I. Meiosis II Sister chromatids separate Stages: Prophase II Metaphase II Anaphase II Telophase II  Prophase II Meiosis II Nucleoli and nuclear envelopes disperse Chromatids shorten and thicken Centrioles move to opposite poles Spindle fibers reform and attach to centromeres  Metaphase II Meiosis II Each of the daughter cells completes the formation of a spindle apparatus. Single chromosomes align on the metaphase plate, much as chromosomes do in mitosis. For each chromosome, the kinetochores of the sister chromatids face the opposite poles, and each is attached to a kinetochore microtubule coming from that pole.  Anaphase II Meiosis II The centromeres separate, and the two chromatids of each chromosome move to opposite poles on the spindle. The separated chromatids are now called chromosomes in their own right.  Meiosis II Telophase II A nuclear envelope forms around each set of chromosomes. Cytokinesis takes place, producing four daughter cells (gametes, in animals), each with a haploid set of chromosomes. Because of crossing-over, some chromosomes are seen to have recombined segments of the original parental chromosomes. Gametogenesis the process in which cells undergo meiosis to form gametes. two cell divisions separate the paired chromosomes in the nucleus and then separate the chromatids that were made during an earlier stage of the cell’s life cycle, resulting in gametes that each contain half the number of chromosomes as the parent. the production of sperm is called spermatogenesis and the production of eggs is called oogenesis. Spermatogenesis occurs in the wall of the seminiferous tubules, with stem cells at the periphery of the tube and the spermatozoa at the lumen of the tube immediately under the capsule of the tubule are diploid, undifferentiated cells. these stem cells, called spermatogonia (singular: spermatagonium), go through mitosis with one offspring going on to differentiate into a sperm cell, while the other gives rise to the next generation of sperm. Oogenesis occurs in the outermost layers of the ovaries. as with sperm production, oogenesis starts with a germ cell, called an oogonium (plural: oogonia), but this cell undergoes mitosis to increase in number, eventually resulting in up to one to two million cells in the embryo