Fig. 1.4.

It shows the process of transcription and translation. Transcription occurs in the nucleus and requires the usage of three polymerase enzymes. RNApol I for rRNA, pol II for mRNA, and pol III for both rRNA and tRNA. RNApol II initiates the process by associating itself with seven transcription factors, TFIIA, TFIIB, TFIID, TFIIE, TFIIH, and TFIIJ. After the synthesis, preRNA transcript undergoes processing to form mRNA by removal of introns by splicing and polyadenylation and capping. Protein synthesis is initiated by formation of ribosome and initiator tRNA complex to initiation codon (AUG) of mRNA and involves 11 factors. Chain elongation occurs after sequential addition of amino acids by formation of peptide bonds. Then polypeptide can fold or conjugate itself to other biomolecules and may undergo posttranslational modifications as glycosylation or phosphorylation to perform its biological functions