Outline the process of transcription. You may use a diagram to illustrate your description. With regards to RNA polymerase, how does transcription differ between prokaryotes and eukaryotes? Transcription is the process of synthesizing messenger RNA (mRNA) from template DNA. There are three stages of transcription. In the initiation phase, the RNA polymerase first binds to the promoter region of the DNA and separates the strands of the double helix to put together RNA nucleotides complementary to the DNA template in a 5’ to 3’ fashion. In contrast to DNA polymerase, it can initiate RNA elongation without a primer.
The RNA transcript is then released from the DNA. What three modifications does eukaryotic mRNA receive during processing? What is the name of the molecular complex that carries out splicing? In RNA processing, both the 5’ and 3’ end of the pre-mRNA are altered. Particularly, the 5’ end receives a modified guanine nucleotide after addition of the first 20-40 nucleotides during RNA elongation. On the other hand, the 3’ end of the pre-mRNA is added with a polyadenylation signal, AAUAAA, and poly-A tail, which is a 50-250 long RNA chain of purely adenine nucleotides.
In addition, certain interior sections of the RNA strand, called introns, are removed, and the remaining ones, referred to as exons, are spliced together. The spliceosome binds to certain sites along an intron to facilitate the latter’ s release and degradation and the joining together of the two exons flanked by the removed intron. Tetracycline is an effective antibiotic because it inhibits protein synthesis. The action mechanism is binding the 30s ribosomal subunit in bacteria, thereby preventing the docking of amino-acylated tRNA.
With your knowledge of the translation process, explain how tetracycline would prevent protein synthesis. If a drug acts by preventing the docking of the amino acid-transporting amino-acylated tRNA, proteins, which are important in all cellular processes, cannot be formed since there is no way by which amino acids can be delivered to initiate elongation of the polypeptide.
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