Question

UAA, UAG and UGA are _________.

• A. Non-overlapping codons
• B. Non-sense codons
• C. Degenerate codons
• D. Chain initiator codons

Answer 1

Answer: (B)

• Non-sense codons are the codons for which no normal tRNA exists. They do not code for any amino acid and their presence leads to their termination of the translation. Eg: UAA, UGA, UAG
  
• Non-overlapping codon means the successive triplets are read in order. Each nucleotide in the sequence is a part of only one codon. Three nucleotides specify one amino acid in a protein. Eg: AUGUUUCGA.... will always code for methionine-phenylalanine-arginine...
  
• Degeneracy of codons means different triplet codons can code for a particular amino acid. Eg: glutamic acid is coded by GAA and GAG. leucine is coded by UUA, UUG, CUU, CUC, CUA, CUG
  
• Chain initiator codon is the first codon of a mRNA transcript translated by a ribosome. AUG codes for methionine, since methionine is the chain initiator amino acid.
  

So, the correct option is 'Non-sense codons'.