Transcription And Translation Flashcards
What generates mRNA?
Tanscription
What produces proteins?
Translation of the mRNA template on ribosomes
What is the central dogma of molecular biology?
Theory that genetic informations flows only in one direction
*DNA — mRNA — protein
Of what is compose a codon?
3 nucleotides sequences
What is the reading frames of the mRNA?
Start codon (AUG) neat the 5’ end
What is the function of stop codons?
Terminate protein synthesis and release the polypeptides
What is the name of the central region of the cell in which prokaryotic DNA resides?
Nucleoid region
What is required for transcription?
The DNA double helix to partially unwind in the region of mRNA synthesis
What is the non template strand?
Complementary to the template strand and almost identical to the coding strand
What is the upstream direction of the DNA?
5’ to 3’ «sense»
What is the initiation site of transcription?
Where the first 5’ mRNA nucleotide is transcribed
In what type of cell the process of translation and transcription occurs at the same time?
Prokaryotes
What is the function of RNA polymerase?
Transcribe all genes and adding nucleotides at the 3’ end of the growing mRNA strand
What are the 5 types of RNA?
-messenger RNA (mRNA)
-Ribosomal RNA (rRNA)
-Transfer RNA (tRNA)
-Snurps
-microRNA
What is the transcription initiation in prokaryotic?
When RNA pol sticks to a promoter sequence and prises open the DNA
What is the function of the promoter?
Initiate transcription by biding with the RNA pol
How is the transcription bubble is made?
When the DNA is unzipped
What facilitates unwinding of DNA template?
-10 region where A-T is rich
What is the process of elongation? In prokaryotic
Release subunits from the polymerase — core enzyme proceed along the DNA template — synthesizing mRNA in 5’ to 3’ direction
How would you qualify the base pair between DNA and RNA?
NOT stable
What is the function of RNA pol during elongation?
Act as a stable linker — ensure elongation is not interrupted
When RNA pol moves down the gene what is he doing?
Adding RNA nucleotides at the 3’ end of the growing messenger RNA strand, using the 3’-5’ template DNA strand
What is the name of the terminator sequence IN PROKARYOTES where the RNA pol drops off the DNA and stops transcribing?
GC hairpin
What is the function of the terminator? In prokaryotic
To drops off the RNA pol and stop transcribing
What are 4 main differences between Prokaryotic and Eukaryotic transcription?
Prokaryote:
-Coupled to translation
-No mRNA processing
-Polycistronic
-Termination =GC hairpin
Eukaryote:
-Separated from translation
-Splice to form mature mRNA
-Monocistronic
-Complex initiation involving transcriptions factors
What means monocistronic?
One promoter for one gene
What means polycistronic?
One promoter for several gene (OPERON)
What are the functions of transcriptions factors?
Proteins necessary to bind to a DNA template in the initiation complex of Eukaryotes transcription
What is the function for RNA pol I in eukaryotes?
Synthesizes all the RNA’s from the duplicated set
What is TATA box?
Promoter region if eukaryotic
What alter how «strongly» the gene is expressed?
Transcription factors, Enhancers and Repressors
What is the function of RNA pol II?
Synthesizes all protein-coding nuclear pre-mRNA
*transcribes the majority of eukaryotic genes
What is the function of coactivators?
Transcription factors that transmit signals from activator proteins to the basal factors
What is the function of Basal transcription factors?
Position RNA polymerase at the start of protein-coding sequence then release the polymerase to transcribe the mRNA
What is the function of Activators?
Regulatory proteins that binds at distant sites = Enhancers
*Activator proteins interact with the complex to increase the rate of
What is the function of FACT protein complex?
Pulls histone away form the DNA template — replaces histones to recreate nucleosomes
What is nucleosomes?
DNA-histone complexes
What is the termination of Eukaryotic transcription?
-RNA pol II takes place beyond the end of the gene being transcribed
What is RNA processing in Eukaryotes?
Steps before the translation to remove introns to make mRNA translatable
What would be the 3 main steps of RNA processing?
1-Pre-mRNA are protected by RNA-stabilizing proteins
2-Addition of signaling factors at the end 5’ and 3’ ends of the molecules
3-Removal of the introns
Where and how the 5’ capping is added?
Added to the 5’ end by phosphate linkage
what is the function of the 5’ capping?
-protects the nascent mRNA from degradation
-helps initiate translations by ribosomes
What are snurps?
Small RNA’s that recognize the introns
What are 3 benefits of the 3’ poly-A tail?
-protects pre-mRNA from degradation
-binding site for protein necessary for exporting mRNA to the cytoplasm
What is the principle of splicing?
Removing introns and reconnecting exons
What is the function of spliceosomes?
Conduct pre-mRNA splicing by complexes of proteins and RNA molecules
What is the basic function of translation?
The ribosomes reads the messenger RNA and assembles amino acids in the correct sequence
How the amino acids are carried to the ribosomes?
By transfer RNA (tRNA)
How does the ribosomes reads the RNA?
By codon, each coding for a specific amino acid
What forms the amine bond?
-amino group (NH2)
-Carboxyl group (COOH)
What is a tRNA?
A strand of RNA that is folded up on itself
What gives the genetic code is bulky structure?
The ability of some tRNAs to match more than one codon
When RNA is double stranded for short sequence what is the quality of the connections between A-U?
Weak connections — only 1 H bond
What is called the activating enzyme?
Amino-acyl tRNA synthetase
What tRNA has that matches the CODON?
Anticodon
What is the codon for Methionine and what would be its anticodon?
Codon: AUG
Anticodon: UAC
In the initiation of translation, what are the functions of the initiation factors?
Positioning the initiator tRNA onto mRNA on the small ribosome subunit
Of what are made ribosomes?
Ribosomal RNA and protein
During the elongation of translation, what is the role of rRNA?
Catalyses the peptide bond formation between the two amino acids
What is the function of the A site?
Binds incoming charged aminoacyl tRNAs
What is the main function of P site?
Binds charged tRNAs carrying amino acids that have formed peptide bonds with the growinfg polypeptides
What is the function of E exit?
Releases dissociated tRNAs so they can be recharged with free amino acids
What occupies the P site at the beginning of elongation phase?
Methiony-tRNA
What are the functions of elongation factors?
Hydrolyse GTP — give energy for each steps
(Translocation to the P site after formation of the peptide bond)
When does the translation termination occurs?
When it encounters a nonsense codon
How polypeptides chains are forming?
Amino group of the amino acids attached to the A site tRNA ——(peptide bond) —— carboxyl group of the amino acid attached to the P-site tRNA
What is the function of peptidyl transferase?
Catalyses each formation of peptide bond
What is the function of releasing factors?
Instruct peptidyl transferase to add water molecule to the carboxyl end of the P-site amino acid
What would be the 4 steps of translation termination?
P-site amino acid detach from its tRNA —- Newly made protein is released — small and large subunits dissociate from the mRNA — Recruited to another translation initiation complex
What are the 3 main steps of gene expression?
Transcription — RNA processing — Translation
What is the benefit of alternative splicing?
Increase the number of gene products form one gene
What is the function of the rER in protein folding?
Protein is destinated to interact with the membrane — ribosomes feeds it into the rER — folds the protein correctly
What is a point mutation?
Mutation affecting a single base pair
What is an example of point mutation?
Substitution
What is a silent mutation?
Mutation happening in a non-coding DNA
What is a nonsense mutation?
Mutation that causes a codon to become a STOP codon
What are 2 example of frameshift mutations?
-insertion
-deletion
What is a frameshift mutation?
Mutation where the resultant protein will be nonfunctional
