Module 2: RNA & Protein Flashcards
______ are the links between genotype and phenotype.
Proteins
_______, the process by which DNA directs protein synthesis, includes two stages: transcription and translation.
Gene expression
_______ is the bridge between genes and the proteins for which they code.
RNA
Eukaryotes also have an intervening step called ________ where pre-mRNA is processed into active mRNA.
RNA processing
What is the major nucleotide difference in DNA and RNA?
DNA = thymine
RNA = uracil
Which of the following is the most abundant?
A. mRNA
B. rRNA
C. tRNA
B. rRNA
Most abundant = rRNA
Least abundant = mRNA
Which of the following is the most unstable?
A. mRNA
B. rRNA
C. tRNA
A. mRNA
Which of the following is NOT a biological role of RNA?
A. Transmission of genetic information
B. Storage of genetic information
C. Catalysis and structural components of macromolecules
D. Gene regulation
E. All of the above are biological roles of RNA
E. All of the above are biological roles of RNA
Which of the following is polycistronic?
A. Prokaryotic mRNA
B. Eukaryotic mRNA
A. Prokaryotic mRNA
prokaryotic mRNA is polycistronic (contains information for more than one polypeptide chain)
Eukaryotic mRNA is monocistronic (contains information for only one polypeptide chain)
______ functions in translation of genetic information from mRNA into proteins.
A. mRNA
B. rRNA
C. tRNA
C. tRNA
Which of the following is highly structured?
A. mRNA
B. rRNA
C. tRNA
C. tRNA
tRNA contains:
- Acceptor stem: where a specific amino acid is linked
- Anticodon loop: base pairs with the codon on mRNA
- Unique nucleotide bases
______ is the structural component of ribosomes.
A. mRNA
B. rRNA
C. tRNA
B. rRNA
______ is an adaptor molecule that carries a specific amino acid to the ribosome/mRNA complex.
A. mRNA
B. rRNA
C. tRNA
C. tRNA
______ is the template for protein synthesis in eukaryotes.
A. mRNA
B. rRNA
C. tRNA
A. mRNA
What are the steps in EUKARYOTIC transcription of DNA-directed RNA synthesis?
- Initiation
- requires binding of protein general transcription factors and RNA polymerase to promoter sites up-stream of the coding region of a gene
- facilitated by transcription factors bound to enhancer sequences at sites far from gene - Elongation
- requires local unwinding of the DNA helix by RNA polymerase
- followed by synthesis of a 5’ to 3’ RNA transcript coded for by the DNA template read in the 3’ to 5’ direction - Termination
- requires a terminal signal sequence that results in release of RNA polymerase and newly synthesized transcript from DNA
Examples of post-transcriptional modification:
- splicing of mRNA to eliminate non-coding introns and join exons
- cleavage and trimming of pre-ribosomal RNAs
- Trimming and modification in tRNA
- Addition of a 3’ poly-A “tail” and a 5’-7-methyl guanosine “cap” to mRNA
What are four examples of eukaryotic post-transcriptional modifications?
- splicing of mRNA to eliminate non-coding introns and join exons
- cleavage and trimming of pre-ribosomal RNAs
- Trimming and modification of tRNA
- addition of 3’ poly-A “tail” and 5’ methyl guanosine “cap” to mRNA
A ______ is a segment of DNA that functions to generate RNA.
gene
_______ catalyze phosphodiester bond formation between the alpha phosphate on the incoming NTP and the 3’-hydroxyl end of the RNA.
RNA polymerase
Which of the following is false regarding prokaryotic RNA polymerase?
A. RNA polymerase (bacterial and eukaryotic) require a primer
B. RNA polymerase do not have either 3’ to 5’ exonuclease activity (proofreading) or 5’ to 3’ exonuclease activity
C. RNA polymerase consists of a core enzyme that contain alpha and beta subunits
D. RNA polymerase contains a holoenzyme which consists of the core plus a sigma
E. All of the above is true regarding prokaryotic RNA polymerase
A. RNA polymerase (bacterial and eukaryotic) require a primer
RNA polymerase do NOT require a primer but do require promoters
note: sigma acts as a regulatory factor, guiding RNA polymerase to specific promoter sequences on the DNA template strand
***Holoenzyme = core enzyme (RNA pol) and sigma
Prokaryotic transcription requires a promoter. What some details regarding the promoter?
Where is the promotor located on DNA?
- the regulatory region of DNA generally located “upstream” of the coding sequence
- contains DNA consensus (-35 and -10 elements) sequences that are recognized by RNA polymerase
- Consensus sequence is a sequence that is mostly found in a given region when multiple sequences are aligned
- Promoters are usually rich in TATA box
What are the steps in prokaryotic transcription?
- initiation begins when sigma binds to promoter region of DNA
- Sigma opens the DNA helix; transcription begins
- initiation is complete: sigma releases; mRNA synthesis continues
- Elongation: transcription continues
- Termination: hairpin forms “downstream”
What promoters do eukaryotes use that is different than prokaryotes?
Eukaryotes = transcription factors
Prokaryotes = sigma
Which of the following eukaryotic RNA polymerases work solely on rRNA?
A. RNA pol I
B. RNA pol II
C. RNA pol III
A. RNA pol I
RNA pol I = rRNA
RNA pol II = mRNA
RNA poll III = tRNA and rRNA
Which of the following eukaryotic RNA polymerases work on both tRNA and rRNA?
A. RNA pol I
B. RNA pol II
C. RNA pol III
C. RNA pol III
RNA pol I = rRNA
RNA pol II = mRNA
RNA poll III = tRNA and rRNA
Which of the following eukaryotic RNA polymerases work solely on mRNA?
A. RNA pol I
B. RNA pol II
C. RNA pol III
B. RNA pol II
RNA pol I = rRNA
RNA pol II = mRNA
RNA poll III = tRNA and rRNA
(T/F)
Eukaryotic rRNA, tRNA, and mRNA are processed but prokaryotic mRNA is generally not processed.
True
***Eukaryotic mRNA processing takes place in the NUCLEUS prior to mRNA translation in the cytoplasm.
Processing of mRNA includes:
- 5’ capping
- 3’ polyadenylation
- Intron splicing (in nucleus)
What is the purpose of 5’ mRNA capping and 3’ polyadenylation?
5’ Capping w/ a modified guanosine is important for:
- stability of mRNA
- exit from nucleus
3’ poly A tailing is addition of A’s to the 3’ end:
- stability of mRNA
- nuclear export mRNA
- transcription termination
- ** translation
Pre-mRNA is spliced to remove _______.
introns
Takes place in spliceosome:
Spliceosome is composed of:
- small nuclear RNAs (snRNAs)
- small nuclear ribonucleoproteins (snRNP) “snRPS”
snRPS cut out introns
Describe alternative splicing:
Production of two (or more) distinct proteins from a single gene.
Individual genes express multiple mRNAs
“you can splice out exons to make different proteins if needed”
________ is an enzyme that synthesizes DNA from viral RNA. This enzyme synthesizes complementary DNA strand (cDNA). This process is extremely error-prone and mutation arise at a high rate, potentially leading to drug resistance.
Reverse transcriptase
What are the 3 stop codons?
UAA, UAG, UGA
There are _____ potential reading frames for a given mRNA sequence.
mRNA = 3
DNA = 6 (three for each strand)
________ refers to prokaryotic mRNAs that often have several coding regions (ORFs) on one mRNA.
Polycistronic
_______ occurs when a change in codon results in change in amino acid sequence.
A. Silent mutation B. Missense mutation C. Nonsense mutation D. Splice site mutation E. Frame-shift mutation
B. Missense mutation
______ occurs when a change in codon does NOT result in a change in amino acid sequence.
A. Silent mutation B. Missense mutation C. Nonsense mutation D. Splice site mutation E. Frame-shift mutation
A. Silent mutation
________ occurs when one or two nucleotide insertion or deletion throws the reading frame out of register resulting in shorter or longer protein with different protein sequence starting at the insertion/deletion site.
A. Silent mutation B. Missense mutation C. Nonsense mutation D. Splice site mutation E. Frame-shift mutation
E. Frame-shift mutation
______ occurs when a change in a codon results in change in amino acid to a stop codon.
A. Silent mutation B. Missense mutation C. Nonsense mutation D. Splice site mutation E. Frame-shift mutation
C. Nonsense mutation
_______ alter the way in which introns are removed producing aberrant proteins.
A. Silent mutation B. Missense mutation C. Nonsense mutation D. Splice site mutation E. Frame-shift mutation
D. Splice site mutation
Silent mutation: change in codon does not result in change in AA sequence
Missense mutation: change in codon results in change in AA sequence (sickle cell)
Nonsense mutation: change in codon results in change in AA to STOP CODON (cystic fibrosis)
What is “Wobble”?
“Wobble” allows one anticodon to base pair with several different codons.
If tRNA anticodon recognized only one codon, cells would have different tRNA for each codon (which they do not)
_______ is the most highly structured of all.
A. mRNA
B. rRNA
C. tRNA
C. tRNA
_________ “reads” the codons.
A. mRNA
B. rRNA
C. tRNA
C. tRNA
note: anticodon of tRNA base pairs with the codon in mRNA in an antiparallel and complementary fashion
______ are a large molecular motor.
Ribosomes
_________ are enzymes that couple (“charge”) amino acids to their cognate tRNA. Correctly pairing the amino acid with the tRNA is important for the proper transmission of genetic information.
Aminoacyl-tRNA synthetases
note: they basically add amino acids to the tRNA by utilizing ATP
________ is a purine rich sequence upstream of AUG start codon that interacts with rRNA to register the reading frame such that INITIATION begins at AUG.
Shine-Dalgarno sequence
Describe each of the following steps in protein synthesis:
- Initiation
- Elongation
- Termination
Initiation:
- small subunit attaches
- tRNA-AA recognizes
- initiation factor is lost when large subunit attaches
A site = Aminoacyl site
P site = Peptidyl site
E site = Exit site
Elongation:
- binding of incoming aminoacyl-tRNA
- Peptide bond formation
- Translocation
Termination:
- stop codon occupies the A site
- Release factors (grenade) hydrolyze the terminal peptidyl bond
- Release of polypeptide
- Dissociation of the ribosome
Describe polysomes:
Many ribosomes will utilize the 1/2 life of mRNA
Which of the following is contains a modified guanosine cap?
A. 5’ end
B. 3’ end
A. 5’ end
***5’ cap
***3’ Poly A tail
