How many rRNA types are found in prokaryotes?
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3 rRNA types.
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How many rRNA types are found in prokaryotes?
3 rRNA types.
What is the initiator tRNA in prokaryotes?
fMet-tRNA.
What is co-translational targeting?
The process where proteins are targeted to the rough endoplasmic reticulum (RER) while they are being synthesized, using a protein called SRP (signal recognition particle)
What is the role of the Shine-Dalgarno sequence in mRNA?
It helps in the binding of mRNA to the rRNA on the ribosome during translation.
What type of mechanism is Rho-independent termination?
Non-enzymatic.
What type of mutations are caused by the insertion or deletion of a base?
Frameshift mutations.
What are tandem triplet repeats?
Repetitive sequences of three nucleotides in DNA that can expand and lead to genetic disorders.
What is the characteristic of repressed chromatin DNA?
It is hypermethylated (heterochromatin).
What are 23S and 28S rRNAs classified as?
Ribozymes.
Major difference between eukaryotic and prokaryotic RNA polymerase?
Prokaryotes have a single RNA polymerase. Eukaryotes have 3 distinct RNA polymerases.
Name disease examples caused by tandem triplet repeats.
Huntington's disease, Fragile X syndrome, Myotonic dystrophy.
What modifications occur in Transfer RNA (tRNA)?
tRNA is spliced, has its 5' and 3' ends trimmed, a CCA sequence added at the 3' end, and bases are modified.
How many RNA polymerases are present in prokaryotes?
A single RNA polymerase.
How many adenylate residues can be added during polyadenylation?
Up to 200 adenylate residues.
Which RNA Polymerase is most inhibited by Actinomycin D?
RNA Polymerase I.
What is the primary function of tRNA?
tRNA functions as adaptor molecules in protein synthesis.
What is the effect of Rifampin on bacterial RNA polymerase?
It inactivates bacterial RNA polymerase.
What enzyme is responsible for peptide bond formation?
Peptidyl transferase.
How many GTPs used in each round of elongation in translation?
3 GTP + 1 ATP for aminoacyl-tRNA activation
What are the key components of eukaryotic mRNA structure?
5' UTR, 5' cap, coding sequence, 3' UTR, and poly A tail.
What is a key feature of eukaryotic mRNA processing?
Addition of a 5' cap and a poly-A tail.
What do enhancers contain in their DNA sequence?
Response elements that bind transcription factors (TFs) to activate gene transcription.
What is the role of the sigma factor (σ) in prokaryotic RNA polymerase?
It provides promoter specificity to the core enzyme.
What is the role of the Spliceosome in eukaryotic cells?
It carries out mRNA splicing.
What is alternative splicing?
A process that allows a single gene to produce multiple mRNA variants by including or excluding certain exons.
What is the role of snRNPs in splicing?
snRNPs are essential components of the spliceosome that facilitate the removal of introns from pre-mRNA.
What are the two types of splicing pathways mentioned?
Single splicing pathway and alternative splicing pathway.
What are polyribosomes?
Multiple ribosomes translating mRNA.
What is the function of DNA intercalating antibiotic agents like Dactinomycin?
They act as transcription inhibitors.
How many rRNA types are found in eukaryotes?
4 rRNA types.
What type of introns are spliced in the GU-AG mechanism?
Type 1 introns.
What are the components of the Spliceosome?
Small nuclear ribonucleoprotein particles (snRNPs).
What are the two main structures of the prokaryotic promoter?
The promoter -35 sequence and the Pribnow box.
What condition is caused by defective GlcNac-P glycosyltransferase?
I-cell disease.
Which type of RNA is not processed in prokaryotes?
Messenger RNA (mRNA).
What toxin inhibits mRNA synthesis by RNA Polymerase II?
α-Amanitin.
What are the functions of the polyA tail in mRNA?
It stabilizes mRNA and assists in the translation process.
Does a prokaryotic or eukaryotic mRNA 5'-end have a phosphate group?
P (Prokaryotic).
If an antibiotic results in the formation of dipeptides, what step is inhibited?
Translocation (diphteria toxin)
What is Rho-dependent termination?
An enzymatic mechanism that employs a hexomeric ATP-dependent RNA-DNA helicase.
What process is the sigma factor necessary for in transcription?
Initiation.
What is a mutation that changes an amino acid codon to a stop codon called?
Nonsense mutation.
Define siRNA.
Short interfering RNA, a class of double-stranded RNA involved in RNA interference.
What is the role of the AAUAAA sequence in polyadenylation?
It is a polyA-addition consensus sequence where cleavage occurs approximately 10-30 nucleotides downstream.
What is a mutation that changes a stop codon to an amino acid codon called?
Frameshift mutation.
What is the function of RNA Polymerase II (Pol II)?
Synthesizes mRNA and most snRNAs.
What is unique about Messenger RNA (mRNA) processing in eukaryotic cells?
mRNA is spliced, capped at the 5' end, and has a polyA tail added at the 3' end.
What is required for polyadenylation?
3' -end cleavage by an endonuclease and poly-A addition by polyadenylate polymerase.
What sequence directs secreted proteins to the ER?
SRP
What is the name for a ribosome binding sequence?
Shine-Dalgarno sequence.
What are the three different nuclear RNA polymerases in eukaryotes?
Pol I, Pol II, and Pol III.
Do RNA polymerases require a primer for synthesis?
No, they do not require a primer.
What does RNA Polymerase III (Pol III) synthesize?
tRNA, 5S rRNA, and some small nuclear RNAs.
What is a mutation that changes a codon without changing the amino acid called?
Silent mutation.
Inhibitory effects of common antibiotics on translation:
Streptomycin: 30S subunit - initiation
Tetracyline: 30S subunit - aminoacyl-tRNA binding
Erythromycin: 50S subunit - translocation
Chloramphenicol: 50S subunit - peptidyl transferase
Puromycin: A site - translocation
What modification targets proteins for degradation?
Ubiquitination.
What process is the Rho factor required for in transcription?
Termination.
Does a prokaryotic or eukaryotic mRNA undergo splicing?
E (Eukaryotic).
Which RNA Polymerase is most sensitive to α-amanitin?
RNA Polymerase II.
Which type of mRNA is an exception to polyadenylation?
Histone mRNAs are not polyadenylated.
Does a prokaryotic or eukaryotic mRNA contain a poly-A tail?
E (Eukaryotic).
What is the sequence required for 3' end polyadenylation of mRNAs?
AAUAA.
Do RNA polymerases have proofreading activity?
No, they do not have proofreading activity.
What is the function of RNA polymerase I?
rRNA synthesis
What cofactor is required for RNA polymerase to do its job?
Mg2+ ions.
What is a key characteristic of eukaryotic promoters?
CAAT box, GC box, TATA box (-25)
Which transcription factor opens the ds DNA and phosphorylates the C-terminal domain of RNA polymerase to initiate transcription?
TFIIH
The series of post-translational modifications on histones that regulate gene activation is known as _____.
Histone Code
Which RNA has the greatest number of base modifications?
tRNA
Region on tRNA where amino acid binds?
CAA
What is the role of N-Acetylglucosamine phosphotransferase?
It is involved in the targeting of enzymes to lysosomes with mannose 6 phosphate
tRNA specificity is due to each tRNA having one ________________.
aminoacyl-tRNA synthetase
How many steps and what is required for the attachment of tRNA to its corresponding amino acid?
2 steps and 1 ATP.
