Molecular Biology: Protein Synthesis: Transcription

Molecular Biology: Protein Synthesis: Transcription
Changes are done, please view the flashcard.

Preview Flashcards

FrontBack
What does mRNA stand for?
 
mRNA stands for messenger RNA.
How is mRNA formed?
 
mRNA is the product of transcription and the template for translation.
How is the 5' cap protected from exonuclease degeneration?
 
The 5' cap is a modified nucleotide linked in a special way to the mRNA. This protects the 5' end from exonuclease degradation.
What protects the 3' end of the mRNA from exonuclease degradation?
 
The poly-A tail protects the 3' end of the mRNA from exonuclease degradation.
What is the structure of eukaryotic mRNA?
 
  • Eukaryotic mRNA: 5' cap - nucleotides - 3' polyA.
Do prokaryotic mRNAs have a 5' cap and polyA tail?
 
No,prokaryotic mRNAs don't have the 5' cap or polyA tail.
What are tRNA (transfer RNA) and rRNA (ribosomal RNA) products of? Do they serve as the template of translation?
 
Both tRNA (transfer RNA) and rRNA (ribosomal RNA) are products of transcription. However, they do not serve as the template of translation.
What are the responsibilities of tRNA and rRNA?
 
tRNA is responsible for bringing in the correct amino acid during translation. rRNA makes up the ribosome, which is the enzyme responsible for translation.
What is the composition of tRNA?
 
tRNA is made of nucleotides, many of which is modified for structural and functional reasons. At the 3' end of the tRNA, the amino acid is attached to the 3'OH via an ester linkage.
What is the structure of tRNA?
 
tRNA structure: clover leaf structure with anticodon at the tip, and the amino acid at the 3' tail.
What is the rRNA made up of?
 
The rRNA is made of nucleotides, many of which is modified for structural and functional reasons.
Why is the rRNA is highly structured?
 
The rRNA is highly structured because it contains the active site for catalysis.
What is the responsibility of the rRNA of the large ribosomal subunit?
 
The rRNA of the large ribosomal subunit is responsible for catalyzing peptide bond formation, and can do this even without ribosomal proteins.
Describe the chain initiation process in the mechanism of transcription.
 
Chain Initiation: RNA polymerase binds to the promoter (TATA box) of the double stranded DNA (closed complex). The double stranded DNA template opens up (open complex).
Describe the chain elongation process in the mechanism of transcription.
 
Chain elongation: nucleoside triphosphates (AUGCs) adds corresponding to the DNA template. No primer is required. RNA elongates as the RNA polymerase moves down the DNA template. RNA is made from the 5' to 3' direction.
Describe the intrinsic chain termination process in the mechanism of transcription.
 
Intrinsic termination: specific sequences called a termination site creates a stem-loop structure on the RNA that causes the RNA to slip off the template.
Describe the Rho (ρ) dependent termination process in the mechanism of transcription.
 
Rho (ρ) dependent termination: a protein called the ρ factor travels along the synthesized RNA and bumps off the polymerase.
How do enhancers affect transcription when bound by Transcription Factors?
 
Transcription factors (proteins) binds to enhancers or silencers (DNA) to affect transcription. Enhancers increase transcription when bound by transcription factor, silencers decrease transcription when bound. Enhancers and silencers in prokaryotes are close to the core promoter, and is part of the extended promoter.
What are Operons?
 
Operons are groups of genes whose transcription can be regulated by binding of either repressors or inducers onto the a stretch of DNA on the operon called the operator.
How do repressors and inducers affect transcriptions?
 
Repressors reduce transcription, inducers increase transcriptions.
What happens when a co-repressor binds to its target?
 
When a co-repressor binds to its target, the resulting complex becomes either an active repressor or an inactive inducer.
What happens when a co-inducer binds to its target?
 
When a co-inducer binds to its target, the resulting complex becomes either an active inducer or an inactive repressor.
What are alpha factors?
 
alpha factors: these are how phages control transcription inside their bacterial host. By making different α factors at different times, the phage can control the correct transcription sequence of early, middle, and late genes. For example, the α factor for late gene is not made until last.
What is transcription attenuation?
 
Transcription attenuation: works in the trp (tryptophan) operon. When tryptophan is scarce and needed, transcription occurs normally. However, if there's already a lot of tryptophan present, then transcription terminates prematurely.
Enter Password

  

Upgrade and get a lot more done!
Upgrade