Lecture on Transcription and Translation

Overview

• Focus on transcription and translation processes.
• Use of the MRNA table for determining amino acids from codons.

MRNA Table

• Codons translate into amino acids.
• AUG: Start codon translates to Methionine (Met).
• UAA, UAG, UGA: Stop codons terminate translation.

Transcription Process

• Gene structure consists of double strands: non-template and template.
• Transcription uses the template strand.
• Example gene sequence: TAC AAT CTG ATC.
• Transcription turns TAC into AUG (RNA uses Uracil instead of Thymine).
• Resulting MRNA sequence: AUG UUA GAC UGA.

Translation Process

• MRNA codons translate to TRNA anticodons.
• Codon-anticodon pairing:
  • AUG (codon) - UAC (anticodon), translates to Methionine.
  • UUA (codon) - AAU (anticodon), translates to Phenylalanine (Phe).
  • GAC (codon) - CUG (anticodon), translates to Arginine.
  • UGA translates to a stop codon.
• Example results in a polypeptide chain with four amino acids.

Using TRNA Information

• TRNA anticodon can help deduce MRNA codon and gene sequence.
• Example anticodon CCU leads to MRNA GGA, translating to Glycine (Gly).
• Gene sequence deduced from MRNA: CCT.

Degenerate DNA Code

• Degenerate: Multiple codons can translate to the same amino acid.
• Example gene sequence: TAC GCT GCG GCA ACT.
• Corresponding MRNA: AUG CGA CGC CGU UGA.
• Amino acid translation:
  • Methionine from AUG.
  • Arginine from CGA, CGC, and CGU.
• Six codons can translate to Arginine (highlighted in pink squares on the table).

Key Takeaways

• Understanding transcription and translation is crucial.
• MRNA tables are essential tools in determining amino acid sequences.
• The degeneracy of the DNA code implies multiple codons can encode the same amino acid, adding redundancy to the genetic code.