Molecular Biology: Cell Division Lesson 3 PDF

Molecular Biology Lesson 3  OBJECTIVES explain the connection between DNA, genes, and chromosomes. distinguish the two types of cell division: mitosis and meiosis recognize the stages which occur during mitosis and meiosis and the remarkable events...

Molecular Biology Lesson 3  OBJECTIVES explain the connection between DNA, genes, and chromosomes. distinguish the two types of cell division: mitosis and meiosis recognize the stages which occur during mitosis and meiosis and the remarkable events that occur during those stages.  ESSENTIAL QUESTIONS What is cell division? What is the connection between DNA, genes, and chromosomes? What is the difference between mitosis and meiosis? What are the different stages of mitosis and meiosis? What events happen in the different stages of mitosis and meiosis? Fundamentals of Molecular Biology GENES VS DNA VS CHROMOSOMES Genes o recognized as the basic physical and functional unit of heredity o units of inherited information o a sequence of nucleotides in DNA or RNA which encodes for the synthesis of a gene product, either RNA or protein. o carrier of the genetic information which determines an organism’s traits, which are features that are passed from the parents to the offspring DNA o stands for deoxyribonucleic acid o a biological molecule that carries the hereditary materials in all living organisms and the genetic instructions which makes all species unique o consists of two strands that wind around each other to form the shape which is known as the double helix o made up of nucleotides linked together via a Hydrogen bond Chromosome o originally coined in German from the Greek words: “khroma”, meaning color, and “soma”, meaning body o condensed structure made up of DNA which carries the genetic material o each chromosome consists of DNA tightly coiled several times around proteins known as histones, in Telomere the end of a chromosome. Telomeres are made of repetitive sequences of non-coding DNA that protect the order to support its structure chromosome from damage. Each time a cell divides, the telomeres become shorter. Eventually, the telomeres become so short that the cell can no longer divide. Chromosome Sequence and visual representation of chromosome in the nucleus of an individual. o there are 46 (23 pairs) of chromosomes inside the human body: o22 pairs are body chromosomes oa pair is for the sex chromosomes (XX in females, XY in males) Chromosome vs Chromatin  Anatomy of Chromosome  CELL CYCLE Cell Cycle o ordered series of events involving cell growth and cell division that produces two new daughter cells o divided into two major phases: (1) Interphase; and (2) M-phase oInterphase – includes three stages: G1, S, and G2 (G0) oM-phase – includes Mitosis and Cytokinesis Cell Cycle: Interphase o the cell undergoes normal growth processes while also preparing for cell division o for a cell to move from interphase into the mitotic phase, many internal and external conditions must be met o recognized as the longest stage in the eukaryotic cell cycle (more or less 24 hours, depends on the organism) o 90% of cells’ life Interphase: 3 stages A. Gap 1 (G1 Phase) ✔Synthesizing its structural proteins and enzymes to perform its functions. ✔cellular contents are duplicated (except chromosomes); growth of the cell ✔checkpoint B. Synthesis phase (S-phase) ✔DNA replication ✔the genetic material is doubled before the cell enters the actual cell division, allowing there to be enough DNA to be split into daughter cells Interphase: 3 stages C. Gap 2 (G2 phase) ✔the cell replenishes its energy, and some of the organelles are duplicated ✔preparation for the actual cell division ✔Checkpoint ✔duplicated chromosomes are checked for error; repairs if needed *Gap 0 ⮚Non-dividing state; can be permanent or not; cell cycle arrest Cell Cycle: M-phase Karyokinesis ✔Division of nucleus (PMAT) Cytokinesis ✔Division of cytoplasm  Cell Division  MITOSIS oFrom the Latin word “mito”, meaning thread o“process of thread movement” oOccurs on somatic or body cells oApparent division; the process by which the nucleus divides to produce two nuclei. Note:  MITOSIS The process produces two daughter 2n cells identical to 2n 2n each other and to the parental cell.  MITOSIS Prophase Metaphase Anaphase Telophase Cytokinesis Prophase ochromatins condense into chromosomes and become visible othe nuclear membrane or nuclear envelope disintegrates ocentrioles duplicate and start producing spindle fibers Metaphase ospindle fibers attach to the centromeres (kinetochore) of the chromosomes oalignment of chromosomes at the middle of the cell (metaphase plate) Anaphase ospindle fibers start to shorten oseparation of chromosomes to chromatids, moving to the opposite poles of the cell Telophase ochromatids reach the opposite poles of the cell and become chromatins onuclear membrane reintegrates oformation of the cleavage furrow Cytokinesis oderived from the Greek words: “cyto”, which means cell ; and “kinesis”, which means motion, cytokinesis can be directly translated as cell movement othe physical process of cell division, which divides the cytoplasm of a parental cell into two daughter cells MEIOSIS oOccurs on sex cells/ gametes/ germ cells oA process by which chromosome number is halved MEIOSIS The process produces n four daughter n n cells that are 2n n different to each n n other and to the parental cell.  INTERPHASE MEIOSIS Prophase I Metaphase I Anaphase I Telophase I Cytokinesis I INTERKINESIS (S-phase) Cytokinesis Prophase II Metaphase II Anaphase II Telophase II II Prophase I odisintegration of the nuclear membrane ocentrioles duplicate and start to produce spindle fibers oFurther divided into 5 stages Crossing Over Metaphase I ospindle fibers attach to the center of homologous chromosomes (kinetochore) ohomologous chromosomes align at the center of the cell Anaphase I the homologous chromosomes are pulled apart and move apart to opposite ends of the cell Telophase I o chromosomes reach the opposite poles of the cell o the nuclear membrane reintegrates o formation of the cleavage furrow o pre-Cytokinesis  INTERKINESIS ✔ Checkpoints ✔ Same process with Interphase but without DNA replication ✔ Cell growth  MEIOSIS II Dubbed as mitosis for haploid cells, because it follows the same key events featured in mitosis Prophase II ochromatins condense into chromosomes and become visible othe nuclear membrane or nuclear envelope disintegrates ocentrioles duplicate and start producing spindle fibers Metaphase II ospindle fibers attach to the centromeres (kinetochore) of the chromosomes oalignment of chromosomes at the middle of the cell (metaphase plate) Anaphase II ospindle fibers start to shorten oseparation of chromosomes to chromatids, moving to the opposite poles of the cell Telophase II ochromatids reach the opposite poles of the cell and become chromatins onuclear membrane reintegrates oformation of the cleavage furrow  ESSENTIAL QUESTIONS What is cell division? What is the connection between DNA, genes, and chromosomes? What is the difference between mitosis and meiosis? What are the different stages of mitosis and meiosis? What events happen in the different stages of mitosis and meiosis?  OBJECTIVES explain the connection between DNA, genes, and chromosomes. distinguish the two types of cell division: mitosis and meiosis recognize the stages which occur during mitosis and meiosis and the remarkable events that occur during those stages. Molecular Biology Lesson 3