Question

A segment of DNA, ‘TTG AGG GGG ATG’ was translated into an oligopeptide with the amino acids, Lysine - Serine - Proline - Tyrosine.

• [(a)] Write the codons in correct sequence for the four amino acids.
• [(b)] If first adenine in DNA is substituted by guanine, what will be the sequence of amino acids in the new oligopeptide?
• [(c)] Write the anticodons for these amino acids.

Hint:

A single base substitution can change the amino acid sequence, affecting protein structure and function.

Answer 1

1. [(a)] Codons for:
   • Lysine: AAA / AAG
   • Serine: UCU / UCC / UCA / UCG / AGU / AGC
   • Proline: CCU / CCC / CCA / CCG
   • Tyrosine: UAU / UAC
2. [(b)] If the first adenine (A) is replaced by guanine (G) in DNA, it will alter the corresponding mRNA codon and amino acid sequence.
   • New amino acid sequence: It would depend on the resulting codons, which might code for different amino acids, possibly altering the peptide chain.
3. [(c)] Anticodons for:
   • Lysine: UUU / UUC
   • Serine: AGA / AGG / AGU / AGC / UCA / UCG
   • Proline: GGA / GGG / GGU / GGC
   • Tyrosine: AUA / AUG