Lecture Notes: Transcription and Translation

Overview

• Discussion on transcription and translation processes using the MRNA table.
• The MRNA table is often provided in exams, indicating which codons map to which amino acids.
  • Example: AUG is a start codon translating to methionine (met).
  • Stop codons: UAA, UAG, UGA terminate translation.

Gene Structure

• Genes consist of double strands: non-template and template.
• During transcription, the template strand is used.

Transcription Process

1. Template Strand Sequence: For example, TAC AAT CTG AT ATC.
2. MRNA Complement: AUG UUA GAC UAU AG.
   • Replace thymine (T) with uracil (U) in RNA.

Translation Process

• MRNA codons are translated into amino acids using the MRNA table.
• Codon examples:
  • AUG translates to methionine (met) with anticodon UAC.
  • UUA translates to phenylalanine (phe) with anticodon AAA.
  • AGA translates to arginine.
  • CUA translates to leucine.
  • UAG is a stop codon.

Example Problem

• Given TRNA anticodon CCU, MRNA codon is GGA.
  • GGA translates to glycine (gly).
  • Gene sequence derived is CCT.

Degeneracy of the DNA Code

• DNA code is degenerate; multiple codons can code for the same amino acid.
• Example: TAC GCT GCG GCA ATC translates to MRNA AUG CGA CGC CGU UGA.
  • Methionine (met) and multiple arginine.
• Arginine can be translated by CGA, CGC, CGU, CGG, AGA, AGG.
• Highlighted in the table with pink squares indicating six codons for arginine.

Key Concepts

• MRNA Table: Essential for understanding translation.
• Degeneracy: Allows for redundancy in genetic coding, ensuring stability.

Important Notes

• Always use the template strand for transcription.
• Remember codon-anticodon pairing and translation to amino acids.