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Lecture on Biochemistry: DNA and RNA

Jul 22, 2024

Lecture on Biochemistry: DNA and RNA

Topics Covered:

  1. Importance in University Examination
  2. Structure and Function of DNA and RNA

Structure of DNA:

  • DNA is composed of units called nucleotides, each consisting of a sugar, phosphate, and nitrogenous base.
  • DNA appears as a double-stranded molecule, with complementary base pairing forming a double helix structure.
  • Nucleotides in DNA are connected by 3'-5' phosphodiester linkages.
  • The strands run in opposite directions (anti-parallel) - 5' to 3' direction.

Components of DNA:

  • Four nucleotides: Adenine (A), Thymine (T), Cytosine (C), Guanine (G).
  • Adenine pairs with Thymine, and Cytosine pairs with Guanine, through hydrogen bonds.
  • Sugar Backbone: Deoxyribose sugar linked to phosphate groups.

Structure of RNA:

  • RNA is typically a single-stranded molecule.
  • Consists of ribose sugar instead of deoxyribose sugar.
  • Four nucleotides: Adenine (A), Uracil (U), Cytosine (C), Guanine (G).
  • Uracil replaces Thymine, pairing with Adenine.
  • mRNA (messenger RNA): Carries genetic information from DNA to the ribosomes for protein synthesis.
  • tRNA (transfer RNA): Transports amino acids to ribosomes during protein synthesis.
  • rRNA (ribosomal RNA): Along with proteins, makes up the ribosomes.

Types of RNA:

  1. mRNA (Messenger RNA)
    • Acts as a template for protein synthesis.
  2. tRNA (Transfer RNA)
    • Brings amino acids to ribosomes.
    • Contains an anticodon region that pairs with codons on mRNA.
  3. rRNA (Ribosomal RNA)
    • Structural component of ribosomes.
  4. snRNA (Small Nuclear RNA)
    • Involved in mRNA processing.
  5. miRNA (Micro RNA) and siRNA (Small Interfering RNA)
    • Involved in gene regulation.

Genetic Code:

  • The sequence of nucleotides in DNA/RNA determines the sequence of amino acids in proteins.
  • The genetic code is triplet-based (codon): Each set of three nucleotides codes for one amino acid.
  • Start Codon: AUG (Methionine) initiates protein synthesis.
  • Stop Codons: UAA, UAG, UGA signal the end of protein synthesis.

DNA Replication and Transcription:

  • DNA Replication: Process by which DNA makes a copy of itself during cell division.
  • Transcription: Process of copying a single strand of DNA into mRNA.
  • Translation: Process where ribosomes synthesize proteins using the mRNA transcript.

Ribosomes & Protein Synthesis:

  • Made of rRNA and proteins, ribosomes facilitate the assembly of amino acids into proteins.
  • Consist of two subunits: Small subunit (30S in prokaryotes, 40S in eukaryotes) and Large subunit (50S in prokaryotes, 60S in eukaryotes).
  • Polyribosome: Multiple ribosomes translating the same mRNA simultaneously.

Importance for Examinations:

  • Understanding of nucleic acids (DNA and RNA) is crucial for exams.
  • Focus on structure, function, and types of RNA.
  • Knowledge of genetic code and protein synthesis mechanisms.
  • Be prepared to explain the processes of replication, transcription, and translation.

Full transcript