Topic 4: Central dogma

Cards (52)

  • Nucleic acids are polymeric macromolecules forming the chemical basis for the transmission of genetic trait
  • Two main classes of nucleic acids
    • deoxyribonucleic acid (DNA)
    • ribonucleic acid (RNA)
  • Nucleotide
    Monomer made of 5-carbon sugar, nitrogenous base, and phosphate group
  • Nucleoside
    Sugar + Base
  • Nitrogenous bases
    • Adenine (A)
    • Guanine (G)
    • Thymine (T)
    • Cytosine (C)
    • Uracil (U)
  • Purines
    Adenine (A) and Guanine (G)
  • Pyrimidines
    Thymine (T), Cytosine (C) and Uracil (U)
  • Base pairing in DNA
    • G ≡ C (3 H-bond)
    • A = T (2 H-bond)
  • Total concentration of purines equals the concentration of pyrimidines in DNA
    1. bonds between nucleotides are the key to the specificity of all nucleic acid-based tests used in the molecular laboratory
  • GC rich region
    Higher melting temperature (Tm)
  • AT rich region
    Lower Tm
  • Nucleotide
    Nucleoside with a phosphate group attached at carbon atom 5'
  • Polynucleotide
    Two nucleotides covalently bonded with a 3'-5' phosphodiester bond
  • General structure of DNA
    • Two polynucleotide strands coiled in a double helix
    • Complementary and anti-parallel sugar-phosphate backbones
    • Bases oriented towards central axis, forming H-bonds and stacking interactions
  • Major DNA conformations
    • A-form
    • B-form
    • Z-form
  • Differences between DNA conformations
    • Helix sense, base pairs per turn, diameter of helix, distance between adjacent base pairs, rotation per base pair
  • Functions of DNA
    • Store genetic information
    • Direct RNA transcription
    • Contain instructions for development, survival, and reproduction
  • Denaturation of DNA

    Loss of the helical structure (double strand to single strand)
  • Methods to denature DNA
    • Thermal denaturation
    • Alkaline method
    • Other denaturing agents
  • Hypochromic effect

    Decreasing ability to absorb light
  • Hyperchromic effect

    Increasing ability to absorb light
  • Melting temperature (Tm)

    Temperature at which half of the DNA molecules are denatured
  • Renaturation of DNA (Annealing)
    Rewinding of denatured DNA strands to form double helix
  • Central Dogma of Molecular Biology

    Genetic information flows from DNA to RNA to protein
  • Transcription
    DNA template to RNA by RNA Polymerase
  • Translation
    RNA to protein
  • Naked DNA is roughly 2 nm in diameter, but the length of a stretched single molecule may be up to several dozens of centimetres
  • DNA compaction in prokaryotes and eukaryotes
    • Prokaryotes: nucleoid-associated proteins
    • Eukaryotes: DNA wrapped around histone proteins to form nucleosomes and chromatin
  • Kingdoms of Life
    • Monera
    • Protista
    • Fungi
    • Plantae
    • Animalia
  • Prokaryotes are classified into Bacteria and Archaea
  • Differences between prokaryotic and eukaryotic cells
    • Presence of membrane-bound organelles, nuclear envelope, cytoskeleton, and complex internal structures in eukaryotes
  • Nuclei
    Eukaryotic nuclei are ~10 μm in diameter and contain 46 chromosomes (2× 3.3G base pairs), consisting of ~2.2 m of DNA in total
  • If DNA is stored naked inside a nucleus or a cell, it would become tangled
  • Prokaryotes
    • Nucleoid-associated proteins resemble the functions of the histone proteins found in eukaryotes
  • Eukaryotes
    • Double helix DNAs are wrapped around spools of histone proteins to form nucleosomes, which package together to produce chromatin
  • Kingdoms of Life
    • Monera
    • Bacteria
    • Archaebacteria
  • A classification for living organisms can be 5-Kingdom or 6-Kingdom
  • Prokaryotic and eukaryotic cells have differences and exceptions
  • Eukaryotes include animal and plant cells