Molecules of Heredity

• Molecules of Heredity


  • Gene
  • DNA
  • Chromosome
  • Nucleus
  • Cell
• Levels of Biological Organization

  • Cell
  • Tissue
  • Organ
  • Organ System
  • Organism
• Gene


  The basic physical and functional unit of heredity and genetic information
• Gregor Mendel


  • Father of genes
  • Performed an experiment with plants in 1857 that led to increase the interest in the study of genetics
• Johann Friedrich Miescher


  • Swiss chemist
  • Discovered a phosphorus-containing substance that was later renamed nucleic acid
• Rosalind Franklin


  • Known for her role in discovering the helical structure of DNA, but was credited to Watson, Crick, and Wilkins who received a Nobel Prize
• Nucleic Acids


  Information molecules that serve as blueprints for the proteins made by cells, and the hereditary material in cells
• Nucleotides


  Monomers that make up nucleic acids
• Nucleotide Synthesis


  1. Dehydration synthesis or polymerization reactions between the sugar of one nucleotide and the phosphate group of a second nucleotide

  2. Forms a sugar-phosphate backbone with phosphodiester bonds
• Components of Nucleotides


  • Pentose Sugar
  • Phosphate Group
  • Nitrogenous Base
• Nitrogenous Bases


  • Pyrimidine Bases (Cytosine, Thymine, Uracil)
  • Purine Bases (Adenine, Guanine)
• Nucleoside


  A purine or pyrimidine nucleobase with a pentose sugar component
• Two nucleotides joined by a phosphodiester bond
• DNA (Deoxyribonucleic Acid)


  Contains a phosphate group, a deoxyribose, and a nitrogenous base
• DNA Base Pairing


  • A of one strand is paired with T on the other
  • G of one strand is paired with C on the other
  • Held together by hydrogen bonds
• Chargaff's Rule


  • The amounts of the bases varied among species, but not between individuals of the same species
  • The amount of A always equalled the amount of T, and the amount of C always equalled the amount of G (A = T and G = C)
• DNA Denaturation


  Loss of helical structure of DNA when the hydrogen bonds between the double strands are disrupted, making the molecule single-stranded
• DNA Renaturation (Annealing)


  The process in which the separated complementary DNA strands can form a double helix again
• DNA Replication


  1. The process by which a double-stranded DNA molecule is copied to produce two identical DNA molecules

  2. Semi-conservative, as each daughter molecule contains one strand from the parent molecule and one new complementary strand
• Enzymes Involved in DNA Replication

  • Helicase
  • Primase
  • DNA Polymerase
  • Exonuclease
  • Ligase
• Leading Strand


  The new strand of DNA that is made continuously, with DNA polymerase adding bases one by one in the 5' to 3' direction
• Lagging Strand


  The new strand of DNA that is made in a series of small chunks called Okazaki fragments, with each fragment started with an RNA primer
• DNA Amplification (Polymerase Chain Reaction)

  1. Denaturation

  2. Renaturation or Annealing

  3. Synthesis or Elongation
• Taq DNA Polymerase


  Commonly used enzyme for DNA Amplification, with an optimum temperature around 75°C
• DNA Repair Mechanisms


  • Base Excision Repair
  • Base Mismatch Repair
  • Nucleotides Excision Repair
  • Double Stranded Break Repair (Homologous Recombination, Nonhomologous DNA End Joining)
• RNA (Ribonucleic Acid)


  Contains ribose instead of deoxyribose, and the base Uracil instead of Thymine

  
• Types of RNA


  • mRNA (Messenger RNA)
  • tRNA (Transfer RNA)
  • rRNA (Ribosomal RNA)
• Differences between DNA and RNA

  • Function
  • Cell Location
  • Strand
  • Sugar
  • Nitrogenous Bases
  • Base Pairing
  • Mobility
• Pentose sugars of RNA and DNA
• Transcription and Translation


  1. DNA replicates its information

  2. RNA polymerase transcribes DNA to produce mRNA

  3. mRNA carries coded information to ribosomes

  4. Ribosomes and tRNA translate the mRNA code to produce proteins
• Codon table showing corresponding amino acids