How Genes Direct the Production of Proteins Flashcards
A strand of DNA copied fully linearly is called a ____.
heteronuclear (hn)/agent RNA
When can the splicing and post-transcriptional modifications occur on the hnRNA after emergence from RNA polymerase II?
immediately
snoRNAs serve as a guide to direct specific ____ of the rRNAs.
modifications (post-transcriptional)
DNA is ___ into RNA.
transcribed
What type of RNA regulates gene expression at the post-transcriptional level?
microRNA
The third base “U” COULD pair with:
A, G, or I
Most protein coding genes are transcribed by ____.
RNA Polymerase II
The third base “C” COULD pair with:
G or I
This antibiotic blocks initiation to elongation.
Streptomycin
mRNA is ___ into protein.
translated
TFIID situates on the gene to create the start site for transcription. What factor does its placement attract?
TFIIB
What kind of bond is formed between the Met-tRNA and the new aminoacyl-tRNA in the A site?
peptide bond
____ process and chemically modify rRNAs.
sno/snRNA
After meeting at the AUG codon, ____ and ____ bind.
the Met-tRNA; the large ribosomal subunit
tRNA transfers ____ to the growing peptide chain.
amino acids
Where would you find free ribosomes?
anywhere in the cytosol
Where are ribosomes assembled?
nucleolus (not a membrane-bound structure)
How many STOP codons must be encountered for translation to halt?
2 consecutive STOP codons
How is the translation of proteins regulated using base pairs?
- base pairing between mRNA codon
- triplet complimentary sequence in tRNA called the anticodon
Why don’t we use tetracycline in children?
because tetracycline loves to bind to mineralized surfaces
Is the genetic code universal for all organisms?
YES
What structure does the small ribosomal subunit recognize and attach to on mRNA?
5’-cap structure
Which antibiotic blocks A-site binding of aminoacyl-tRNA?
Tetracycline
What type of structure does miRNA form to block protein synthesis? What enzyme does it utilize?
a hairpin structure (complementary base pairs folded in on itself); “Dicer” enzyme
An Argonaute, facilitated by Dicer, is a mature _____.
miRNA
What is it called when more than one codon can make the same amino acid?
degenerate
How many RNA Polymerase II molecules can work on copying a gene simultaneously?
A BUNCH!
Which nucleic acid would be more useful when sequencing the genome of an ant fossilized in amber?
DNA - more stable than RNA due to deoxyribose properties
A 3 base sequence is a ____.
codon
Can gene transcription proceed in opposite directions?
YES - since template for genes is always 3’-to-5’ the strand can just flip flop since it’s DNA
What is the role of transcription factors?
to park RNA polymerase II appropriately on the DNA strand in order to initiate and complete transcription starting at base 1
Which antibiotic blocks the peptidyl transferase reaction, thereby preventing elongation?
Chloramphenicol
rRNA comes from a ____.
gene
____ directs the proper cleavage of introns and allows the ligation of exons.
snRNA
What are the three STOP codons?
UAA, UAG, UGA
What types of RNA processing must wait until the primary strand is complete?
capping, polyadenylation
What happens after the initiation of helicase activity by TFIIH in DNA transcription?
ATP is expended; phosphorylation of the C-terminal RNA polymerase II occurs; TF disassembled; polymerase opens into active conformation; transcription occurs
If you were to put DNA and RNA into a solution with a pH of 10, which would degrade first and more quickly?
RNA - very unstable in alkaline conditions
Synthesis of new DNA (aka RNA strand) is always ____; the template (DNA) runs ____.
5’-to-3’; 3’-to-5’
What would likely be the cause of closely similar or analogous genes being located in totally separate regions of the body?
alternative splicing of mRNA at some point in development (driven by developmental cells signals hormones, environmental signals, etc.)
A number of antibiotics we use to treat infections target ____ and ____.
transcription; translation
What happens in the elongation step of translation?
synthesis of the peptide chain
What gets pushed out of the A site and P site by the ribosome? What gets pushed into the P site?
A site - dipeptide
P site - “empty” tRNA
*P site - peptide
Do UTRs or non-translated regions get translated?
NO; but they do get transcribed
At which codon and amino acid does translation start?
AUG; methionine
rRNA encodes _____.
ribosomal proteins
Of these components, which is/are used to synthesize the sequential protein?
(cap : 5’ UTR : coding sequence : 3’ UTR : polyA tail)
coding sequence
Which type of RNA turns off gene expression by directing the degradation of mRNAs?
siRNA
What happens after the binding of TFIID and TFIIB?
TFIIH binds, which has helicase activity
What disassembles from the RNA polymerase II transcriptional complex after phosphorylation of RNA pol II?
transcription factors (TFIID, TFIID, TFIIH)
Why are bacterial cells able to replicate so much faster than eukaryotic cells?
because mRNA can be translated to proteins SIMULTANEOUSLY with transcription of DNA to RNA
In individuals affected with Roberts Syndrome, there is ____ rDNA to rRNA transcription, which leads to decreased ____.
decreased; protein synthesis
What is mRNA translated into?
proteins
Which part of the DNA sequence get translated into the amino acid sequence of the protein.
exons
Genes that are essentially the same but found in different regions of the body are ____.
isoform genes
What transcription facto recognizes the TATA box, specifically its subunit?
TFIID; TBP
The RNA polymerase II has to be properly ____ on the start site of transcription.
phased
What molecule is created by the “charging” of tRNA with the specific mRNA codon? What enzyme catalyzes this?
aminoacyl-tRNA; aminoacyl-tRNA synthetase
TFIIH does what in the initiation of transcription?
acts with helicase activity to unwind DNA at transcription start point; phosphorylation of RNA polymerase II
What is the role of TFIIB?
to position RNA polymerase II on the DNA strand correctly
___ do get translated; ___ get transcribed, but not translated.
Exons; introns
Does splicing occur simultaneously with transcription?
YES
Mature mRNA is exported to the ____ or ____ via nuclear bound proteins.
cytoplasm; cytoplasmic ER
miRNA binds to the RISC complex (RNA-inducing silencing complex), which suppresses ____ and promotes ____.
protein synthesis; mRNA degradation
RNA splicing is performed by the ____, a complex made up of snRNAs and proteins in a SNP complex.
spliceosome
Where does transcription occur?
nucleus of eukaryotes
What factor binds first to the TATA box?
TFIID (w/ subunit called the TBP - TATA box binding protein)
mRNA is transcribed from a ___.
gene
At which point of transcription and translation does export to the cytoplasm occur?
post-translationally **after DNA has been transcribed into mRNA (after polyadenylation at 3’ end - AAAA)
Do all proteins contain methionine in their sequence?
NO, because post-translational modifications occur and may take methionine out or cleave bits off
When does splicing take place?
before the maturation of mRNA
How do cells achieve their specialized functions?
based on:
expression of specific genes
post-translational modifications (glycosylation, phosphorylation) of resulting proteins
What does RNA Polymerase II transcribe?
mRNA
Where would you find membrane-bound ribosomes?
rough ER (associated with membrane proteins and may be secreted out of the cell)
A strand of unprocessed RNA containing introns an exons is referred to as ____.
hnRNA
Where are proteins synthesized? Where does translation take place?
cytoplasm of cell in eukaryotes
mRNA is read by the ribosomal machine as a ___.
codon
miRNA is a _____ repressor.
translational
Which antibiotic prevents RNA synthesis?
Rifamycin
Response elements are ___ when referring to their structure.
promoter regions
What happens in the termination step of translation?
synthesis stops and protein is released from the ribosome
Gene expression can be regulated by transcription factors that bind to:
promoter elements in DNA and/or
proteins that are bound to these promoter elements
Translation starts at the ___ end of mRNA.
5’
What is the purpose of polyadenylation (addition of polyA tail)?
stabilizes the RNA since it is more easily degraded than DNA
Which is the most abundant RNA in a cell?
rRNA (mRNA is only 3%!)
What are the 4 steps of translation?
Activation
Initiation
Elongation
Termination
What kind of RNA regulates gene expression by blocking the translation of specific mRNAs?
microRNA
What happens in the initiation step of translation?
binding of ribosome to 5’-end of mRNA
subsequent binding of initiator Met-tRNA (AUG)
This antibiotic blocks the ribosome exit channel and inhibits elongation.
Erythromycin
_____ are sequences in the DNA that direct or promote the transcription of a gene.
Promoters
What happens in the activation step of translation?
the formation of aminoacyl-tRNAs
Where would you find the TATA box on a strand of DNA?
about 25 base pairs before the start site of transcription
Is at the translational level the same as at the post-transcriptional level?
YES
What is the obligatory first step in the initiation of TBP/TFIID and RNA polymerase II binding?
the presence or absence of specific transcription factors
In both prokaryotes and eukaryotes, how many strands of DNA are transcribed into RNA?
1
Which base in the triplet codon is the LEAST specific?
the third base (allows “wobble”)
