Finals-mRNA processing Flashcards
The 3’ end of pre mRNAs undergoes endonucleotic cleavage while 3’ end of a mature mRNA transcript undergoes addition of a poly A tail
true
which of the ff sequences are not recognized by a number of RNA-binding proteins and RNA processing enzymes for mRNA processing?
a. AAUAAA polyadenylation/cleavage sequence
b. CA sequence
c. GU rich or U rich sequence
d. TATA
D
(T/F) the gene sequence that specifies the 3’ ends of mature mRNA molecules and sites for poly A addition are transcribed as part of the pre mRNA
true
___ an RNA binding protein that binds AAUAAA consensus sequence in 3’ end of eukaryotic mRNA
cleavage and polyadenylation specificity factor (CPSF)
_____ an RNA binding protein that binds the GU rich region of the 3’ end of eukaryotic mRNA
cleavage stimulation factor F (Cstf)
(T/F) the CA sequence at the 3’ end of mRNA is recognized by either CPSF or Cstf
false
recognized by another factor involved in cleavage of 3’ tail prior to poly A addition
(T/F) the first step in the initial mRNA 3’end processing is the binding of CPSF and Cstf to attract additional proteins that function with them
false
this is the second step
(T/F) CPSF and Ctsf (of RNA pol II C-terminal) hop onto nascent premRNA 3’ end as it is synthesized by Pol ll during the initial steps of mRNA 3’ end processing
true
this is the first step!
(T/F) Cleavage of 3’ end occurs and is the 3rd step in the initial mRNA 3’end processing
true
_____ the enzyme that adds about 200 A nucleotides onto 3’ end produced by the cleavage of 3’ end of mRNA
poly-A-polymerase
(T/F) Addition of poly-A
tail requires a template and encoded by a gene
false
does not require a template and thus is not encoded
by gene
(T/F) Poly-A-binding
proteins bind to poly-A
tail and remain attached as mRNA leaves nucleus
true
(T/F) Poly-A-binding
proteins assist in initiation phase of protein translation of the mRNA
true
which of the ff is not bound to mRNA as it is exported from the nucleus?
a. poly-A-binding proteins
b. CBC (cap-binding complex)
c. hnRNP
d. SR proteins
none of the above. all are bound to mRNA`
(T/F) Components of the nuclear pore can recognize the bound factors on mRNA and passively transport only mature and intact mRNA out of the nucleus
false
ACTIVELY transports it. the rest is true
____ the most abundant form of RNA in cells and form the core of ribosomes
rRNA
(T/F) prokaryotes and eukaryotes use one RNA Pol to synthesize all RNAs
false
only applies to bacteria
euks have specialized pols
(T/F) RNA Pol l is similar in structure to RNA Pol ll in all aspects
false
RNA pol 1 lacks a C terminal tail, lack a 5’ cap or poly A tail
____ eukaryotic RNA used specifically for production of rRNAs
RNA pol I
(T/F) lack a 5’ cap or poly A tail of RNA Pol l transcripts help a cell distinguish noncoding RNAs (e.g., rRNA) from coding RNAs (mRNA)
true
(T/F) one mRNA transcribed from a gene may be translated many times. the same is true for structural RNAs
false
true for mRNAs but rRNA must occur in abundance
(T/F) human cells contain about 200 rRNA gene
copies/haploid genome in small clusters spread over five different chromosomes
true
_____ are the four types of eukaryotic rRNAs that are each present as a single copy per ribosome
18S, 5.8S, 28S, and 5S
(T/F) 18S, 5.8S, and 28S rRNAs are derived from a single chemically modified mRNA
false
large 45S rRNA precursor
(T/F) the 45S rRNA precursor is modified by methylation of many 2’OH groups on nucleotide sugars and isomerization of many uridine nucleotides to guanine
false
uridine to pseudouridine
(T/F) 5S rRNA is transcribed from a different set of genes by RNA Pol lll and is not chemically modified
true
(T/F) snoRNAs complexed with proteins to snoRNPs direct modification and cleavage of 45S rRNA precursor
true
_____ the structure where Ribosomal subunits are produced and contains rRNA genes, precursor and mature rRNAs, rRNA processing enzymes, snoRNPs, ribosomal proteins, and ribosomal subunits in all stages of
assembly
nucleolus
(T/F) the nucleolus is bound by a membrane
false
(T/F) U6 snRNP for splicesome and telomerase are produced in nucleus
false
in NUCLEOLUS
(T/F) Although rRNA genes occur in clusters on different chromosomes , the gene clusters are concentrated in nucleolus
true
which of the ff is not involved in the translation process?
a. Synthesis and assembly of ribosomes
b. Proper coupling of each amino acid to its appropriate tRNA
c. Transcription and transport of mRNA out of nucleolus
d. Interactions between mRNA and amino acid bound tRNAs (aminoacyl-tRNAs) with ribosomes
C
transport out of NUCLEUS
which of the ff does not apply to the genetic code?
a. is a triplet code (codon)
b. establishes the “rules” by which genetic information can be translated into a sequence of amino acids
c. is degenerate
d. codons are always written 3’ to 5’
D
5’ to 3’
which of the ff does not apply to codons?
a. are degenerate
b. one codon can code for more than one amino acid
c. are always written 5’ to 3’
d. some codons do not code for aa
B
this is false. codon is not ambiguous
1 aa = coded by one or more codons
but 1 codon = 1 aa
____ describes the arrangement of the third base in a degenerate codon
wobble base
*___ acts as initiation codon that is present at the start of all translated proteins and specifies the aa methionine
AUG codon
(T/F) A mutation that alters the third base will not have any effect on the amino
acid at that position
true
coz codons are degenerate
(T/F) codons that have a “T” at the second position code for hydrophobic aa thus, mutations in first or third positions of these codons will only substitute another hydrophobic amino acid at that position
false
“U” base. no T in mRNA
the rest is true
*(T/F) one codon codes for more than one amino acid
false
genetic code is NOT ambiguous
which of the ff does not apply to the genetic code?
A. Prokaryotes use the same genetic code as humans
b. Mitochondria have their own small genomes and machinery
c. the mitoC is dependent on the cell machinery
d. tryptophan is the mitoC’s universal UGA stop codon
C
(T/F) One mRNA sequence could generate three different amino acid
sequences that encodes actual protein sequence
false
only one reading frame encodes a protein
____ are clover shaped molecules that act as adaptor molecules which literally match amino acids with their respective codons in mRNA (physically)
tRNAs
(T/F) tRNAs fold into its shape thtough hydrogen bonding
false
intramolecular base pairing
_____ set of three consecutive nucleotides in tRNA region that binds to complementary nucleotides in the codons of mRNA
Anticodon
(T/F) A short region at the 3’ end of the tRNA is attached an amino acid that corresponds to the codon in mRNA
true
____ and ___ are modified bases in tRNA
pseudouridine and
dihydrouridine
____ polymerase that transcribes tRNA
RNA pol III
(T/F) Some tRNA precursors in both prokaryotes and eukaryotes contain introns that are spliced
true
(T/F) tRNA, like mRNA do not contain lariat formation and its reaction is catalyzed by proteins
false
applies to tRNA ONLY
(T/F) About 10% of all nucleotides in ALL tRNA are modified version of either A, C, U, or G
true
(T/F) non covalent modifications occur after normal nucleotides are incorporated into the tRNA
affects both conformation of tRNA and pairing of anticodon with codon
false
this is COVALENT
(T/F) humans have hundreds of tRNA genes that represents only about 48 anticodons
true
497 tRNA genes = 48 anticodon
(T/F) wobble interactions or atypical covalent bonding enable a number of tRNAs are capable of pairing with several codons
false
wobble interaction is thru atypical hydrogen bonding
(T/F) Wobble occurs in tRNAs that only require accurate pairing with first two bases of a codon but can accept a mismatch at third or wobble position
true
*(T/F) 5’ base of tRNA
anticodon that pairs with 3’ base of mRNA codon
true
which of the ff does not apply to the codon-anticodon interaction?
a. Inosine at wobble position can pair with A, C, or T in the codon
b. 5’ base of tRNA
anticodon that pairs with 3’ base of mRNA codon
c. a given tRNA can recognize multiple codons for the same amino acid
d. wobble interactions occur thru atypical hydrogen bonding)
A
inosine = A, C or U
no T in mRNA
____ is formed when an aa is coupled to its appropriate tRNA
aminoacyl-tRNA
(T/F) formation of aminoacyl-tRNA is the activation step in protein synthesis
true
____ catalyzes the amino acid activation step in protein synthesis
aminoacyl-tRNA synthetase
____ is formed when aa is coupled to AMP by aminoacyl-tRNA synthetase
aminoacyl-AMP
(T/F) aminoacyl-tRNA is formed when aminoacyl moiety is transferred to tRNA
true
*(T/F) Cells contain a different synthetase for each type of amino acid
true
20 of them!
(T/F) overall coupling reaction requires hydrolysis of ATP
true
____ the process where the aminoacyl is moved from 2’OH to 3’ OH of ribose in a aminoacyl tRNA synthetase reaction
transesterification
______ the only tRNA is used in protein synthesis
3’-O aminoacyltRNA
_____ & ____ are the essential adaptor molecules that convert nucleotide sequence into an amino acid sequence
aminoacyl-tRNA synthetase and aminoacyl-tRNA
and think about their function!
(T/F) AminoacyltRNA
synthetases recognize specific binding sites on tRNA molecules and almost always involves the anticodon
false
anticodon is a component but not always involved. the rest is true
(T/F) large amino acids have a high affinity to its Aminoacyl-tRNA
synthetase active site
false
larger =does not fit active site = lower affinity
(T/F) for aa very close in size, the correct amino acid is allowed entry into the pocket of its synthetase and exclude the incorrect aa
false
correct aa = excluded
incorrect aa = enters pocket = removed from enzyme
(T/F) a protein is synthesized from its N-terminal to its C-terminal
true
(T/F) Throughout protein synthesis, the carboxyl end remains attached to a tRNA molecule to form a peptidyl-tRNA molecule that is broken and formed for each new aa addition
true
which of the ff is not true about ribosomes in the cell cytoplasm?
a. Protein synthesis occurs on ribosomes
b. Ribosomes of prokaryotes and eukaryotes are similar in structure and function
c. composed of one large and one small subunit
d. small subunit catalyzes the formation of peptide bonds to form the protein
D
large subunit does this
small subunit = scaffold for base pairing of tRNA and mRNA
(T/F) Ribosomal subunits are only joined when synthesizing proteins
true
which of the ff is not true?
a. Subunits associate with each other on an mRNA molecule , usually near its 5’ end
b. Rate of addition of nucleotides in ribosomes is same in prokaryotes and eukaryotes
c. The mRNA is pulled through ribosome such that its codons are accessible to
incoming charged tRNAs in active site of ribosome
d. Translation continues until a stop codon in mRNA is encountered then ribosomes separate
B
2 amino acids/sec in eukaryotes
20 amino acids/sec in
prokaryotes
(T/F) Ribosomes contain three RNA-binding sites but binds only two RNAs at a time
false
four binding sites, the rest is true
_______ catalyzes the formation of a peptide bond between the amino acids in protein synthesis
peptidyl transferase
(T/F) The carboxyl end of the polypeptide chain is detached from the tRNA at the A site and is joined to the free amino group of the amino acid linked to the tRNA at the P site by the formation of a peptide bond
false
detached from P site, linked at the A site
which of the ff is false?
a. formation of peptide bond occurs in the large subunit of the ribosome
b. aminoacyl-tRNA
binds to the vacant A site of the ribosome
c. A tRNA with attached growing polypeptide chain is located in the adjacent E site
d. elongation process in translation is associated with conformational changes in the ribosome
C
in the P site
(T/F) viruses use the same genetic codes as humans and prokaryotes
False
Viruses are not organisms. But they use the same genetic code (? Clarify)
(T/F) mRNA is read 5’-3’ direction
True
