Lecture Notes: Nucleic Acids

Introduction to Nucleic Acids

• Nucleic acids, including DNA and RNA, are crucial polymers in the body, alongside proteins and carbohydrates.
• DNA gives organisms their identity and understanding its processes can aid in combating diseases like cancer.

Structure of Nucleotides

• Nucleotides are the monomers of nucleic acids and consist of three parts:
  1. Monosaccharide: Either D-ribose or 2-deoxy-D-ribose.
     • D-ribose found in RNA; 2-deoxy-D-ribose found in DNA.
     • Difference based on hydroxyl presence at carbon 2.
  2. Heterocyclic Base: Contains nitrogen, forms either purines or pyrimidines.
     • DNA bases: Adenine (A), Guanine (G), Cytosine (C), Thymine (T).
     • RNA replaces Thymine with Uracil (U).
  3. Phosphate Group: Attached to carbon 5 of the sugar.

Nucleosides

• Combination of sugar and base, named based on the base (e.g., adenosine, 2-deoxyadenosine).

Nucleotides

• Addition of a phosphate group to the nucleoside.
• ATP and cyclic AMP are examples of nucleotides.

Formation of Nucleic Acids

• Nucleotides are linked by phosphate esters between the 3' hydroxyl of one and the 5' hydroxyl of another.
• Forms a sugar-phosphate backbone with bases protruding, allowing for sequence representation (e.g., GCAT).

DNA Structure and Base Pairing

• Base Pairing: A-T and C-G pairings due to complementary base-specific hydrogen bonding.
  • A-T pairs form two hydrogen bonds, C-G form three.
• DNA exists as two anti-parallel strands forming a double helix.
  • Strands run in opposite directions: 5' to 3' and 3' to 5'.

RNA Structure

• Typically single-stranded, composed of ribose sugars.

DNA's Role and Storage

• DNA encodes genetic information in every cell.
• Length: Single-cell DNA can stretch over a meter; collective DNA stretches to the solar system.
• Chromosomes: DNA coils around histones, undergoes supercoiling to form compact chromosomes.
• Chromatin: The collective genetic material in cell nuclei.

Conclusion

• Understanding nucleotide structure and DNA double helix aids in comprehending DNA functionality.

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