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• Nucleic Acids:

  • Chemical repositories of genetic information
  • Located inside the nucleus (for eukaryotes) or in the nucleoid region (for prokaryotes)
  • Biopolymers of nucleotides linked together by phosphodiester bonds
  • Two forms: DNA (2’-deoxyribonucleic acid) and RNA (ribonucleic acid)
• Nitrogenous Bases:

  • Flat aromatic rings
  • Basic
  • Have conjugated double bonds
  • Have multiple sites for hydrogen bonding
• Purines:

  • Adenine (A)
  • 6-aminopurine
  • Guanine (G)
  • 2-amino-6-oxypurine
• Pyrimidines:

  • Cytosine (C) – 2-oxy-4-aminopyrimidine
  • Thymine (T) – 2,4-dioxy-5-methylpyrimidine (or 5-methyluracil)
  • Uracil (U) – 2,4-dioxy-pyrimidine
• Nucleotides:

  • Sugar + base + phosphate
  • Naming convention: sugar-base-phosphate (e.g., 2’-deoxyadenosine-5’-monophosphate - dAMP)
• DNA (Deoxyribonucleic Acid):

  • Linear sequence of deoxyribonucleotides
  • Two complementary strands held together by hydrogen bonds
  • Backbone: Alternating sugar and phosphate groups linked by phosphodiester bonds
  • Forms a double helix structure
  • Right-handed helix with major and minor grooves
• RNA (Ribonucleic Acid):

  • Mostly single-stranded polynucleotides
  • Sugar: ribose
  • Bases: A, C, G, U
  • Can form RNA-DNA hybrids and secondary structures like stem-loop and cloverleaf structures
• DNA Packaging in the Cell:

  • Helps compactly pack DNA in the nucleus
  • Chromosomes composed of chromatins (DNA + associated proteins)
  • Histones and non-histone chromosomal proteins involved in DNA packaging
  • Nucleosomes: 147 bp supercoiled DNA wrapped around histone octamer
  • Chromatin fiber models: solenoid and zigzag
  • Looped domains and non-histone protein scaffold
• Credits:

  • Dr. Neilyn O. Villa
  • Asst. Prof. Joseph Carmelo K. San Pascual
  • Copyright 2023
  • Genetics and Molecular Biology Division, Institute of Biological Sciences, College of Arts and Sciences, University of the Philippines Los Baños, College, Laguna 4031, Philippines