Protein Synthesis Processes

Central Dogma of Molecular Biology

• Involves DNA replication, transcription, and translation.
• Crucial for understanding protein synthesis.

Transcription

• Definition: Process where a DNA template is read to produce a messenger RNA (mRNA).
• Enzyme: RNA polymerase is key in transcription.
  • Attaches to DNA, separates double-stranded DNA at hydrogen bonds.
  • Moves along template strand, attaches RNA nucleotides forming mRNA.
  • mRNA detaches after transcription, DNA recombines.
• Base Pairing Rules: Guanine pairs with cytosine; adenine pairs with uracil (in RNA).
• Important Terms:
  • Gene: Section of DNA that is transcribed.
  • Coding Strand: Strand of DNA to make mRNA copy (sense strand).
  • Template Strand: Opposite strand read by RNA polymerase (anti-sense strand).
• Gene Expression: Transcription occurs when a gene needs to be expressed.
  • Different cells express different genes (e.g., neurons & skin cells).
  • Important for cell differentiation and development.

Translation

• Location: Occurs in the cytoplasm.
• Components: mRNA, ribosomes, tRNA molecules.
• Process:
  • Ribosome reads mRNA to create a polypeptide chain.
  • tRNA molecules bring amino acids to the ribosome.
  • Ribosome reads mRNA codons (sets of three bases) to specify amino acid order.
  • Translation begins at start codon, ends at stop codon.
  • Genetic code is universal and degenerate.
• Ribosome Sites: EPA sites - Aminoacyl, Peptidyl, Exit.
• Codon and Anticodon: Codon on mRNA, anticodon on tRNA.
  • 64 possible codons, but only 20 amino acids.
  • Genetic code is degenerate due to overlapping codons.

Mutation Impacts

• Mutations can change DNA, affecting protein function.
• Example: Single point mutation in DNA can alter protein structure, e.g., sickle cell disease.
  • Some mutations have no effect due to code degeneracy.

Study Strategy

• Familiarize with codon tables for exams.
• Practice transcribing DNA to mRNA and determining amino acid sequences.