Transcription

• Central Dogma is a process by which genetic information in DNA are converted into functional protein that reveals the instructions in DNA
• Transcriptions and Translation are the 2 processes that involve in concept of central dogma
• Transcription is a process where the genetic information stored in DNA is copied or transcribed as RNA nucleotide sequences
• Transcription occurs in nucleoid in prokaryotes, while nucleus in eukaryotes
• mRNA growth of the chain is 5' to 3'
• The 2 strands of DNA involve in transcription are sense and antisense strand. But the sense strand is the only one DNA strand needed to transcribe
• Antisense strand is the template (non-coding) strand of DNA that serves as the template for RNA synthesis during transcription. Runs from 3' to 5' direction
• Sense strand is the coding strand of DNA that has the same sequence as the RNA transcript (except with thymine instead of uracil in RNA). But doesn't directly participate in mRNA synthesis. Runs form 5' to 3' direction
• Products of transcription are mRNA, tRNA, rRNA, RNA Primer, and etc.
• 3 steps of transcription are initiation, elongation, and termination.
• 4 component of transcription are sigma factor, RNA polymerase, promoter, and terminator
• The goal of initiation step is to find promoter, and it is found by RNA polymerase assisted by sigma factor
• The 3 major product of transcription are mRNA, tRNA, and rRNA. In addition, tRNA and rRNA are product that is stable in highly acidic environment and other factors due to have secondary structure and ability to recycle
• Promoter is the specific sequence of where transcription process begins. Within promoter, there are 2 highly conserve regions located: Prokaryotes promoter have Pribnow Box and -35 Region, while eukaryotes promoter have TATA box.
• Pribnow box or -10 region: a region located 10 bases before the start of transcription and its base sequence are TATAAT
• -35 region: a region located 35 base upstream from the start site of transcription and its base sequence are TTGACA
• Sigma Factor: Assistant of RNA polymerase that recognized the 2 highly conserve region of the promoter where RNA polymerase bound to it
• Sigma Factor: A removable subunit of RNA polymerase that associated/assisted only in the initiation process, then dissociated in the initiation complex
• Initiation complex is a state where RNA polymerase binds to the DNA template strand assisted by a sigma factor, and it is also where the promoter is located
• Alternative Sigma Factor is multi-domain subunit of RNA polymerase for specific group only under special treatment
• RNA Polymerase: An enzyme that is responsible for transcribing or copying the DNA into mRNA by complementary
• Terminator: A specific sequence in DNA template that terminated or where the transcription process end
• Archaea and Eukarya have similar structures when it comes to RNA polymerase
• RNA polymerase's proofreading function is less efficient in DNA polymerase, but independent when unwinding the DNA strand which does not require helicase
• mRNA is a product of transcription which carry a protein blueprint from cell's DNA needed to translate and a single stranded RNA that is complementary to the DNA nucleotide sequence.
• mRNA has a short half-life due to its primary structure, energy conservation, and self-protection mechanisms, which make it prone to degradation due to interaction with the innate immune system within the cell.
• mRNA molecule in prokaryotes is polycistronic that have more than 1 gene to encodes in single promoter and terminator because all at once as a single mRNA producing 2 or more proteins by later be cleaved into individual polypeptides which does not contain introns.
• mRNA molecule in eukaryotes is monocistronic that contain only one gene to be encode producing one protein. Containing conding (exons) and noncoding (introns) regions.
• An mRNA encoding a GROUP of COTRANSCRIBED GENES is called polycistronic mRNA
• Operon: a group of related genes cotranscribed as a polycistronic mRNA
• The Archaea contained only a single RNA polymerase, resembles eukaryotic polymerase II
• 3 process in post-transcription in mRNA to make matured mRNA and also add protection needed for translation process: capping polyadenylation, and splicing
• Capping is the a process that add guanine base via unusual 5' to 5' triphosphate linkage.
• Prokaryote capped partially or not modified further but retains the 5' triphosphate, while eukaryote capped or modified at the 5' end.
• This addition of guanine in mRNA protect from degradation, exonucleolytic activity (in eukaryotes), and mark the mRNA as "self" product of the cell to avoid innate immune system recognition.
• Polyadenylation is a process that add poly(A) tail in the 3' end of mRNA to make as a matured mRNA and protect when transporting from nucleus/nucleoid into cytoplasm (rough endoplasmic reticulum in eukaryotes). More stable and prevent also from degradation
• Splicing is a process/ability of an enzyme called spliceosome that cleaved or excised out the noncoding region(introns) of mRNA. Related in polycistronic mRNA in prokaryotes
• Shine-Dalgarno Sequence: a conserved nucleotide sequence found in prokaryotic mRNA molecules, particularly in bacteria and was made by two scientists, Howard D. Dalgarno and Marilyn E. Shine, in the 1970s.
• rRNA is a product of transcription and a component of ribosome (a protein-synthesizing organelle) which help to translate mRNA sequence to an amino acid sequence.
• Svedberg Unit: A unit of time that is equal to 10 raised to the power of -13 seconds, used to expressed sedimentation coefficients