Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
87 Cards in this Set
- Front
- Back
RNA polymerases (do/do not) require a primer.
|
do not
*must recognize a start point for transcription and a DNA strand to use as a template |
|
RNA polymerases synthesize mRNA from DNA in the _________ direction.
What building blocks does this require (4)? |
5' to 3'
ATP, GTP, CTP, & UTP |
|
RNA polymerases lack a ____________________ activity.
|
3' to 5' exonuclease activity
|
|
Bacterial cells have (a single/multiple) RNA polymerase(s).
|
a single
|
|
What are the 4 subunits of the E.coli core RNA polymerase enzyme? What binds to this core enzyme and directs the enzyme to bind at a promoter?
|
alpha2-beta-beta prime
sigma |
|
Describe the three eukaryotic RNA polymerases.
|
1. Polymerase I produces rRNA
2. Polymerase II produces mRNA 3. Polymerase III produces tRNA and 5s rRNA They all have the same mechanism of action but recognize different promoters |
|
RNA polymerase binds to the _________ on DNA.
|
promoter
*promoter, promoter-proximal elements, & enhancers are all regulatory sequences on genes |
|
The start point and termination signal on DNA are contained in the...
|
coding region, located after the promoter
|
|
What DNA strand, coding or template, is used by RNA polymerase to make mRNA?
|
template strand
|
|
The _________ strand of DNA is the same sequence as the mRNA strand except T's are replaced with U's (there are no T's in RNA).
|
coding
|
|
During translation, where can you find the codons?
|
they are the sequence of 3 nucleotides found on the mRNA, read from 5' to 3'
|
|
The AT rich consensus sequence in E. coli that determines the start of transcription is called the...
|
Pribnow box
|
|
The AT rich consensus sequence in eukaryotes that determines the start of transcription is called the...
|
TATA box
|
|
In addition to the TATA box, you can find consensus sequences such as the _______, ________, and _________ in eukaryotes.
|
CAAT box, GC-rich sequences, enhancers
|
|
When DNA is unwound by the RNA polymerase holoenzyme, what enzyme is used to remove supercoils?
|
DNA topoisomerase
|
|
Termination of transcription at the termination signal through the formation of a hairpin loop in DNA is called...
|
Rho-independent transcription termination
|
|
Termination of transcription through the binding of rho factor is called...
|
Rho dependent transcription termination
|
|
The unit of a promoter and all the genes it controls is called an
|
operon
|
|
mRNA generated from an operon containing many genes produces a _____________ transcript.
|
polycistronic
*cistron is a region of DNA that encodes a single polypeptide chain |
|
In bacteria, ___________ allows the coupling of transcription and translation.
|
the absence of a nucleus
|
|
Many transcription factors, nucleosome-modifying complexes, chromatin remodeling complexes, elaborate transcript modification through splicing are all processes found in...
|
eukaryotic cells (more elaborate than bacterial cells)
|
|
Eukaryotic mRNA usually contains information for (one/many) polypeptides.
|
one
|
|
____________ interact w/ each other and RNA pol II to initiate transcription.
|
General transcription factors (GTFs)
*promoters contain GTF binding sites |
|
____________ bind elements to help stimulate transcription initiation.
|
Enhancers
*can be far from promoter |
|
Pol II synthesizes a primary transcript of mRNA. The initial mRNA transcript is capped at the _____ end.
|
5'
|
|
The 5' end cap of mRNA serves as a...
|
recognition site for binding to ribosome and decreases degradation
|
|
The initial mRNA transcript is processed to have a poly A tail at the _____ end (for stability). The poly A tail is added by the ____________ enzyme.
|
3' end
poly(A) polymerase |
|
Toxin alpha-amanitin blocks _________ and is fatal at low doses.
|
RNA polymerase II
|
|
Introns are removed from premature mRNA by...
|
splicing
|
|
Describe the progression of rRNA transcripts to their final cleaved forms.
|
First you make a 45S precursor rRNA strand from a set of tandemly repeated genes on DNA. This large transcript gets cleaved into 18S, 28S and 5.8S rRNAS.
|
|
What 4 things must be done to immature tRNAs before they can leave the nucleus?
|
1. cleavage of 5' and 3' ends
2. splicing of intron 3. replacement of 3' UU with CCA 4. Modification of bases |
|
Thalassemias are caused by mutations that affect the synthesis of __________.
|
alpha or beta chains of hemoglobin
|
|
Mutations that cause beta thalassemias are found in the...
|
TATA box (w/i promoter), reducing the accuracy of the transcription starting point
|
|
There is only one codon combination for ___________ and ___________.
|
-Trp
-Met (start codon) |
|
tRNA's bind amino acids at their ______ end and transport them to the ribosome.
|
3'
tRNA is a link btwn mRNA codon and specific AA |
|
The ________ of the tRNA interacts with the codon of mRNA.
|
anticodon
|
|
tRNAs recognize (one/more than one) codon per amino acid. This property is called the ____________
|
more than one
wobble hypothesis *reason fewer than 61 tRNAs required |
|
In a silent mutation, a changed codon may code for
(point mutation, one base altered) |
the same amino acid
|
|
In a missense mutation, a changed codon may code for
(point mutation, one base altered) |
a different amino acid
|
|
In a nonsense mutation, the changed amino acid may code for
(point mutation, one base altered) |
termination (stop codon)
|
|
Sickle-cell anemia is caused by a (missense/nonsense/silent) mutation.
|
missense
|
|
In sickle-cell anemia, the amino acid _____ replaces the normal amino acid ______.
|
Val replaces Glu
(GAG) (GTG) |
|
In translation, ATP is used to...
|
attach AA onto the tRNA
|
|
In translation, GTP is used to...
|
bind the aminoacyl-tRNA to the A site and for subsequent translocation
|
|
mRNA is translated from its 5' end, producing a polypeptide synthesized from its _______ terminal.
|
amino
|
|
Prokaryotic mRNA is polycistronic while eukaryotic mRNA is __________.
|
monocistronic
(mRNA codes for only one polypeptide chain) |
|
The attachment of amino acids to tRNA is catalyzed by specific ______________ and requires _______.
|
aminoacyl-tRNA synthetases, requires ATP
|
|
Aminoacyl-tRNA synthetases have a high fidelity of translation due to their ________ and ______ activities.
|
specificity
proofreading (only enzyme that proofreads) |
|
In order, the 3 sites where tRNA binds on the ribosome are the..
|
1. A site (initial binding)
2. P site 3. E site (exit) |
|
In prokaryotes, the 16S rRNA contains a sequence that is complementary to the ___________ sequence of mRNA. The binding of these 2 sequences positions mRNA on the _________.
|
-Shine-Delgarno
-30S subunit |
|
In eukaryotes, what subunit binds to the cap structure of mRNA?
|
40S
|
|
In prokaryotes, the initiator tRNA carries a ________________.
|
N-formylated methionine
|
|
In eukaryotes, the initiator tRNA carries a ______________.
|
regular methionine (not formylated)
|
|
During elongation, amino acids are added to the __________ terminus of the growing chain. This addition is catalyzed by the enzyme _________.
|
carboxyl
peptidyltransferase |
|
During translation, the first tRNA (initiator tRNA of the AUG start codon) enters the ___ site.
|
P site (NOT A!)
|
|
Elongation of the amino acid chain continues until a _________ is read at the A site, causing _________ to hydrolyze the bond between the peptide and tRNA as well as the binding of _________.
|
stop codon
peptidyltransferase release factors |
|
Gene transcription is mostly regulated on the level of __________.
|
transcription
|
|
_____________ can target mRNA for degradation.
|
small interfering RNA
|
|
In prokaryotes, the chaperones that are members of the heat-shock protein family that help the growing protein to fold are __________ and _________.
|
DnaJ and DnaK
|
|
In eukaryotes, the chaperones that are members of the heat-shock protein family that help the growing protein to fold are __________ and _________.
|
Hsp40 and Hsp70
|
|
When a new protein is folding, disulfide bonds are formed between ______ residues by the __________ enzyme.
|
Cys
disulfide isomerase |
|
Posttranslational modifications: Ser, Thr, and Tyr can be
|
phosphorylated or dephosphorylated
(phosphorylation most common modification) |
|
Posttranslational modifications: Lys and Arg can be
|
methylated (methylation of histone is involved in regulation of transcription)
|
|
Posttranslational modifications: Pro and Lys can be
|
hydroxylated (Stabilization of collagen)
|
|
Posttranslational modifications: how is blood coagulated (clot formation)?
|
carboxylation
|
|
Posttranslational modifications: the attachment of fatty acids does what?
|
anchors proteins in membrane
|
|
Posttranslational modifications: Ser, Thr, or Asn residues of membrane or secreted proteins can be...
|
glycosylated
|
|
Posttranslational modifications: Lys in carboxylases can be
|
biotinylated
|
|
What is needed for the translation of proteins on the ER surface for insertion into the ER?
|
A signal peptide is translated--this attracts a SRP (signal recognition particle) that stops translation, binds the ribosome to the SRP receptor on the ER, and translation then resumes
|
|
Amino acids synthesized in the cytosol that are destined for the nucleus contain a...
|
nuclear localization signal
|
|
Amino acids synthesized in the cytosol that are destined for the mitochondria contain a...
|
mitochondria entry signal
|
|
Proteins destined for secretion outside the eukaryotic cell are synthesized on the...
|
ER surface and then released inside the ER
|
|
Why do we need transcription?
|
to protect DNA from cytoplasmic environment (eukaryotes)
cell does not have enough copies of genome to serve cell's metabolic needs to regulate the rate of protein synthesis (control mRNA #, life-time, and RNA binding factors) |
|
Describe the structural elements of the gene and their function in transcription
|
Promoter sequence of DNA binds RNA polymerase and proceeds coding region. Coding region contains start point and termination signal for transcription
|
|
Difference between template and coding strand
|
coding strand is used to determine AA sequence
template strand is used to produce mRNA -they are complementary and antiparallel to one another |
|
Describe the role of transcription factors in initiation of transcription
|
Transcription factors bind to promoters and interact with each other and RNA pol II to initiate transcription. Enhancers bind to transcription factors to make transcription MUCH more efficient.
|
|
Differences between eukaryotic and prokaryotic primary transcripts
|
In prokaryotes transcription & translation are coupled, no nucleus
In eukaryotes, more transcription factors, 3 RNA polymerases, modification of transcript, uncoupled, occurs in chromatin w/i nucleus Eukaryotic Transcription: 1. initiation 2. elongation 3. termination 4. posttranslational modification |
|
Explain the function of Cap structure and poly-A tail in eukaryotic mRNA
|
Cap structure decreases degradation (5' end)
poly A tail provides stability (3' end) *coding region w/ introns & exons btwn cap and tail |
|
Discuss the consequences of mutations in noncoding regions on the gene expression (use thallasemia as example)
|
promoter region mutation, reduces starting point accuracy, leads to lower level of mRNA
|
|
What do mutations in coding regions result in?
|
-nonsense, frameshift, missense mutations yeild unstable or inactive proteins
-splice-site mutations result in aberrantly spliced mRNA -3' processing site mutations result in failure to polyadenylate mRNA |
|
Characteristics of genetic code (4)
|
1. specificity
2. universality 3. redundancy 4. nonoverlapping and commaless |
|
___________ binds to the 30S subunit and distorts its structure, interfering with the initiation of protein synthesis.
|
streptomycin
|
|
___________ interact w/ small ribosomal subunits, blocking access of the aminoacyl-tRNA to the mRNA-ribosome complex.
|
tetracyclines
|
|
____________ a component of the 50S ribosomal subunit, transfers the AA from the P site onto the AA at the A site & catalyzes peptide bond formation.
|
peptidyltransferase
|
|
_______________ inhibits prokaryotic peptidyltransferase. High levels may also inhibit mitochondrial protein synthesis.
|
Chloramphenicol
|
|
_________ and ________ bind irreversibly to A site on the 50S subunit of the bacterial ribosome, thus inhibiting translocation.
|
clindamycin and erythromycin
|
|
_________ inactivates the eukaryotic elongation factor, eEF-2, thus preventing translocation.
|
diptheria toxin
|