How is DNA used to build proteins including: transcription, post transcript processing of mRNA (introns and exons), translation, and post-translation processing of proteins ?
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Transcription: requires a template (usually double-stranded DNA), ribonucleoside triphosphates (ATP, GTP,UTP,CTP), the enzyme RNA polymerase and divalent metal ions.
Translation: during the translation process proteins are made by the ribosomes on the mRNA strand. The main steps in translation are: (a) activation of amino acids, (b) transfer of the amino acid to tRNA, (c) initiation of synthesis, (d) elongation of the polypeptide chain and (e) chain termination. The 20 amino acids (aa) used in protein synthesis are activated by ATP in the presence of specific activating enzymes called aminoacyl synthetases to form aminoacyle adenylates (aaa), also called aminoacyl AMP.
Post-transcription processing: primary transcription is often larger than the functional RNAs. It is called heterogeneous or hnRNA especially in case of mRNA. Post trancription processing is required to convert primary transcript into functional RNAs.
Splicing: Eucaryotic transcripts possess extra segments (introns or intervening sequences). The functional coding sequences are called exons.
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