Gen bio

• Cell Reproduction


  Fundamental process to create life, occurring in all forms of it, ensuring the perpetuity of their existence, as well as growth, tissue replacement, and reproduction in multicellular organisms
• Cell Reproduction


  Cell division, where each cell divides to form two daughter cells. There are three biological mechanisms: binary fission, meiosis, and mitosis
• Cell Reproduction Mechanisms


  • Binary fission
  • Meiosis
  • Mitosis
• Cell Cycle


  Definite stages of growth, duplication, and division
• Cell Cycle


  1. Interphase (Gap 1, Synthesis, Gap 2)

  2. Cell Division (Karyokinesis and Cytokinesis)
• Interphase


  Growth period in the cell cycle, divided into Gap 1, Synthesis, and Gap 2 stages
• Gap 1 (G1) Stage


  • First part of interphase where cell carries out normal metabolic functions and increases in size and organelle number
  • Longest stage of interphase
• Synthesis (S) Stage

  • Second part of interphase where cell makes a copy of genetic material (DNA)
• Gap 2 (G2) Stage

  • Cells continue normal functions and undergo further growth, contains a critical checkpoint before transitioning to next stage
• Mitosis


  Division of nucleus into two genetically identical nuclei containing the same full set of DNA, occurs in body cells except sex cells
• Mitosis


  1. Prophase

  2. Metaphase

  3. Anaphase

  4. Telophase
• Prophase


  • Chromatin condenses to form chromosomes, individual chromosomes become visible as threadlike structures, nuclear envelope breaks down
• Metaphase

  • Spindle fibers attached to kinetochore of sister chromatids facilitate movement of chromosomes to middle of cell, chromosomes line up at metaphase plate
• Anaphase

  • Spindle fibers shorten to pull sister chromatids to opposite ends of cell
• Telophase


  • Reverse of major events in prophase occurs, microtubules and spindle fibers disintegrate, nuclear membrane starts to form, chromosomes uncoil
• Cytokinesis


  Formation of cleavage furrow pulled away by microfilaments, splitting cytoplasm into two cells, equal portions of parent cell's plasma content to daughter cells
• Cellular biology
• Meiosis


  Another process of cell division that takes place in sexually mature organisms
• Meiosis


  1. Results in the reduction of the chromosome number from diploid to haploid in the germ cells (egg and sperm cells)

  2. Gametes have one set of chromosomes
• Meiosis


  • Successful completion ensures the genetic continuity of species
  • Sexual reproduction also results in genetic variety of the members of a species
• Meiosis


  Two divisions: Meiosis I (reduction division) and Meiosis II (Interkinesis)
• Meiosis I


  1. Prophase I

  2. Metaphase I

  3. Anaphase I

  4. Telophase I
• Prophase I


  • Nuclear membrane and the nucleolus start to disappear
  • Spindle fibers and replicated chromosomes during interphase are visible
  • Dyad (chromosome with two sister chromatids held together by a centromere)
  • Pairing of homologous chromosomes
• Homologous Chromosomes


  • Chromosomes with the same length, staining pattern and position of the centromere
  • Carry the same genes but different alleles or type (one from mother, one from father)
• Prophase I


  1. Crossing over takes place between two non-sister chromatids along a point called chiasma

  2. During crossing over, the other two chromatids remain uncrossed

  3. Pair of homologous chromosomes – composed of four sister chromatids called tetrad
• Metaphase I


  1. Paired homologous chromosomes (tetrads) are moved by the spindle fibers to the equator of the cell

  2. Spindle fibers increase in number and attach to the kinetochore of each chromatid

  3. Kinetochore- the protein complex assembled at each centromere, serves as the attachment site for spindle microtubules
• Anaphase I


  1. Homologous pairs of chromosomes (dyads) separate and migrate toward their respective poles

  2. Sister chromatids are still attached at their centromere, move toward the poles

  3. 46 double-stranded chromosomes equivalent to 92 chromatids
• Telophase I


  1. Two daughter cells are completely divided during telophase I

  2. Nuclear envelope and nuclei reappear, chromosomes (less visible)

  3. Each daughter cell has 23 chromosomes
• Interkinesis


  • A short pause between meiosis I and meiosis II
  • It is similar to the interphase of mitosis except that, here there is no replication of chromosome
• Meiosis II


  1. Prophase II

  2. Metaphase II

  3. Anaphase II

  4. Telophase II
• Prophase II


  1. Nuclear envelope and nucleoli disappear

  2. Chromatids start to shorten and thicken

  3. Centrioles move to opposite poles, spindle fibers arrange in preparation for metaphase

  4. 23 chromosomes (46 chromatids)
• Metaphase II


  1. Characterized by the movement of chromosomes to the cell equator

  2. Each chromosome has two sister chromatids joined together by a centromere and are attached to the spindle fiber
• Anaphase II


  1. Centromeres joining the chromatids divide, allowing microtubules to attach to the kinetochores to pull the sister chromatids apart

  2. Sister chromatids are now called sister chromosomes
• Telophase II


  1. Nuclear membrane around the chromosomes of each daughter cells form

  2. Chromosomes uncoil and lengthen

  3. Cleavage furrow

  4. Four new cells with haploid chromosomes (23 chromosomes) are produced
• Biomolecules


  Very large molecules formed by polymerization, where monomer subunits form covalent bonds to form polymers
• Four types of macromolecules

  • Proteins
  • Carbohydrates
  • Lipids
  • Nucleic Acids

  
• Monomer


  Smaller molecules or subunits of a complex molecule
• Polymer


  A macromolecule consisting of a series of monomers bonded together
• Dehydration reaction


  A reaction in which small molecules are assembled into large molecules by removing water

  
• Hydrolysis reaction


  An organic chemical reaction that involves adding water to break apart molecules