Cell Division

• Cell Division - process by which a cell divides to form two new cells
• Binary Fission - divides forming two new identical cells in prokaryotes
• Mitosis and Meiosis - happens within Eukaryotes
• Mitosis - process that cells use to make exact replicas of themselves and replaces and repairs damaged cells
• Meiosis - formation of sex cells or gametes
• 3 Major steps of Binary Fission - DNA replication, Chromosome Segregation, Cytokinesis (Separation)
• DNA Replication - DNA is copied resulting into two identical chromosomes
• Chromosome Segregation - chromosomes separate and move towards ends (poles) of cell
• Cytokinesis (Separation) - cytoplasm divides forming 2 cells
• Cell Cycle - sequence of events from the time a cell first arises as a result of cell division until the time when that cell itself divides
• 2 Main periods of cell cycle - Interphase and Mitosis phase
• 3 Phases of Interphase - G0, G1, S, G2
• G0 Phase - cell neither divides nor prepares itself for the division (resting stage)
• G1 Phase - the cell is metabolically active and grows continuously during this phase
• S Phase (synthesis) - DNA replication occurs
• G2 Phase - protein synthesis occurs and preparation for cell division
• Mitosis Cell Division - division of somatic cells in eukaryotic organisms
• 4 Sub-phases of Mitosis - Prophase, Metaphase, Anaphase, Telophase
• Prophase - the membrane around the nucleus dissolves, releasing chromosome
• Metaphase - chromosomes are aligned vertically at the center of the cell
• Anaphase - the sister chromatids separate from each other
• Telophase - a membrane forms around each side of the cell producing nuclei
• Cytokinesis - separation of 2 nuclei
• Genetic Terminology: Ploidy - number of sets of chromosomes in cells
• Haploid - contains only 1 copy of chromosome "n"
• Diploid - contains two sets of chromosomes "2n"
• Genetic Terminology: Homologues - chromosomes exist in homologous pairs in all diploid cells except in sec chromosomes in male (XY)
• Meiosis - singular cell divides twice to produce 4 cells containing half of the original amount of genetic information
• Interphase I - 2 chromosomes with sister chromatic each. 2 centrosomes are found outside the nucleus
• Prophase I - recombination or crossing over will occur. the nuclear membrane dissolves
• Metaphase I - the chromosome will align horizontally at the center of the ccell
• Anaphase I - the chromosomes are pulled by spindle fibers which brings 1 chromosome to the other side of the cell and the remaining chromosome to the other
• Telophase I and Cytokinesis - a membrane forms around each set of chromosome. Separation of 2 nuclei
• Prophase II - the membrane around the nucleus dissolves, centrosome will duplicate
• Metaphase II - the chromosome in each nuclei will align at the center
• Anaphase II - sister chromatid are pulled by spindle fibers which brings 1 chromatid to the other side of the cell and the remaining chromatid to the other
• Telophase II and Cytokinesis - a membrane will form around each set of chromosomes
• Jacob's syndrome - genetic condition in which a human male has an extra male (Y) chromosome, giving a total of 47 chromosomes instead of the more usual 46
• Turner Syndrome - occurs when the number of chromosomes is 45 with only one copy of the X chromosome
• Sex-linked traits - originate from genes on sex chromosomes