DNA base pairing mnemonics

Course Logistics

  • Enrollment assistance for the class
    • If you are still trying to get into the class, email Dr. Alija Mujic at amujic@csufresno.edu with:
    • Your Student ID number
    • A note that you are in Dr. Hsu’s lecture section, Tue/Thu 11:00–12:15
    • Your preferred lab day/time you have been attending
    • At least two other lab times you would be willing/able to attend
  • Upcoming deadlines and exam dates
    • Fri, Sept 12 at 11:59 – Research Deconstruction Activity due (5 questions; class will cover today)
    • Mon, Sept 15 at 11:59 PM – Homework #3 – Macromolecules
    • Tues, Sept 16 at 11:00 AM – Exam 1
  • Materials and testing requirements
    • You may have: a calculator (graphing calculators OK; cell phone calculators not allowed)
    • Scratch paper
    • LockDown Browser required for Exam 1
    • Exam length: 55 minutes, 40 questions
    • You must check in with the instructor (with a photo ID) before leaving; you may leave after check-in
  • Unit 1 focus and schedule
    • Exam 1 will cover ALL SIX TOPICS in Unit 1
    • Sept 11: Finish Nucleic Acids Research Deconstruction; apply Unit 1 concepts
    • Sept 16: Exam 1
    • Sept 18: Hannah Gill (from Dr. Emily Walter’s research group) to visit and discuss a study on how Biology 1A students learn; short pre-survey participation is voluntary but feedback helps improve Biology teaching
    • Be present on Sept 18 to hear details and decide whether to participate

Unit 1: The Chemistry of Life (Macromolecules) and Nucleic Acids

  • Macromolecules overview
    • Major classes: carbohydrates, lipids, proteins, nucleic acids
    • Focus on properties, functional groups, carbon skeleton, and how monomers assemble into polymers
    • Macromolecules in Biology: important in structure and function of cells
  • Nucleic Acids: learning goals
    • Identify the function of DNA and RNA
    • Identify parts of a nucleotide
    • Explain how nucleotides are bonded to form polynucleotides
    • Identify a purine and a pyrimidine; describe base pairing in DNA
    • Describe the structure of the DNA double helix
    • Contrast DNA and RNA; distinguish an RNA nucleotide from a DNA nucleotide
    • Determine the complementary sequence to a DNA or RNA sequence
  • Nucleotides: structure and components
    • Nucleotide = nucleic acid building block; composed of three parts:
    • Nitrogenous base
    • Pentose sugar (ribose in RNA; deoxyribose in DNA)
    • Phosphate group
    • Nucleoside = sugar + base (no phosphate)
    • Phosphodiester bond links nucleotides; dehydration synthesis forms the backbone
    • DNA sugar is deoxyribose; RNA sugar is ribose
  • Nucleosides vs nucleotides examples
    • Adenosine (nucleoside)
    • Adenosine monophosphate (AMP) (nucleotide)
  • Stereochemistry and numbering in nucleic acids
    • 5' carbon bears the phosphate group; 3' carbon bears a hydroxyl group (OH)
    • Important for synthesis of new DNA and RNA
    • Atoms are numbered in nucleotides and sugars; assign α, β, γ phosphates for triphosphates used in polymerization
    • 2' carbon: hydroxyl in RNA; hydrogen in DNA
  • Nucleic acids polymerization and directionality
    • Nucleic acids form by nucleotide addition in the 5' → 3' direction
    • The 5'-phosphate of the incoming nucleotide donates an OH that joins with the 3'-OH of the preceding nucleotide to form a phosphodiester bond
  • The nucleic acid building block: the nucleotide
    • 5' end carries a phosphate group; 3' end has a hydroxyl group
    • Phosphate group connects sugars via phosphodiester linkage; overall polymer is nucleic acid (DNA or RNA)
  • DNA structure and base pairing
    • DNA is a double-stranded molecule; strands run antiparallel
    • Nitrogenous bases pair via hydrogen bonds: A pairs with T via 22 hydrogen bonds; C pairs with G via 33 hydrogen bonds
    • Base-pairing rules ensure complementary sequences
    • Purines (A, G) are larger; pyrimidines (C, T, U) are smaller; A-T and C-G pairing preserves uniform width
  • DNA sequencing example and antiparallel orientation
    • Example 1: 5'-ACGGTCTTCCAG-3' pairs with 3'-TGCCAGAAGGTC-5'
    • Alternative representation of the bottom strand: 5'-CTGGAAGACCGT-3' (demonstrates antiparallel pairing)
  • Purine-pyrimidine concept and mnemonics
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