(a) AUG codes for methionine and is initiator codon.
(b) Some amino acids are coded by more than one codon and hence code is degenerate. For example, phenylalanine or Phe is coded by UUU as well as by UUC.
The code in nearly universal, meaning, from micro-organism to human beings, codon would code for same amino acid. For example, UUU would code for Phe from bacteria to human (though some exceptions are found in mitochondrial codons and in some protozoans).
(c) Aminoacylation of tRNA is first phase of translation where amino acids are activated in presence of ATP and linked to ir cognate tRNA. An aminoacyl tRNA syntase is an enzyme that attaches appropriate amino acid onto its tRNA. Enzyme and AMP are released. tRNA complexed with an amino acid is sometimes called charged tRNA. The amino acid is linked to 3'-OH end of tRNA through its -COOH group.
AA-AMP + t + tRNA --> AA-tRNA + AMP + Enzyme
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