Summarize the process of RNA synthesis transcription by usin

Summarize the process of RNA synthesis (transcription) by using the following terms: template, promoter, RNA polymerase. rRNA, mRNA, tRNA, terminator. (Know what each term means.)

Solution

Eukaryotic transcription: The three steps in eukaryotic transcription inside the nucleus of a cell include the following.

1. Initiation; 2. Elongation; 3. Termination

Initiation: Transcription is the process of synthesis of RNA from DNA template in the presence of RNA polymerase inside the nucleus. Transcription is initiated by the binding of transcription factors and RNA polymerase II in eukaryotic cell nucleus where promoter region (GC rich region, TATA box) of DNA is located. Promoters are base pair sequences of DNA that potentially enable binding of RNA polymerase II to initiate transcription by unzipping the DNA for protein synthesis.

TATA-binding Protein (TBP): TATA-less promoters promotes transcription by promoting RNA polymerase type II using other factors such as nuclear proteins Transcription factor TFIIA during the transcription of DNA. Pre-initiation complex formed by TBP in the eukaryotic DNA (A- T rich TATA box absent) 35 nitrogen bases upstream followed by DNA melting due to formation of negatively charged bonding with DNA backbone using arginine and lysine amino acid residues of TBP. In this manner DNA –TBP protein interaction promotes transcription-using type II RNA polymerase using other transcription factors such as SL1, TFIIB, TFIIC, and TFIID.

Elongation: Synthesis of mRNA is going to takes place from 5 prime to 3 prime region with transcription factors & RNA polymerase. Complementary nucleotides are synthesized onto the RNA in which thymine i sreplaced by uracil

Termination: Termination of transcription is going to happen based on factor dependent & factor independent manner. In case of factor dependent manner, transcription termination factors (terminators) such as ribosomal DNA repeats present at the ribosomal intergenic spacer region that trigger termination.

mRNA: It is produced by the transcription of DNA in the presence of RNA polymerase enzyme and it has amino acid coding exons to code for specific proteins as per genetic code.

rRNA (ribosomal RNA): It has 50S and 30S ribosomal subunits which have aminoacyl site and peptidyl site to carry out translation process during protein synthesis with mRNA.

tRNA (transfer RNA): It has clover leaf structure & common to all tRNA structure. It has anticodon site to bind to the mRNA and to displace mRNA transcript from nuclear region onto the rRNA for protein synthesis. It is considered as an adaptor molecule mainly consist of 76 to 90 ribonucleotides in length