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Biochem 2 > Finals-mRNA processing > Flashcards

Finals-mRNA processing Flashcards

1
Q

The 3’ end of pre mRNAs undergoes endonucleotic cleavage while 3’ end of a mature mRNA transcript undergoes addition of a poly A tail

A

true

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2
Q

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

A

D

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3
Q

(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

A

true

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4
Q

___ an RNA binding protein that binds AAUAAA consensus sequence in 3’ end of eukaryotic mRNA

A

cleavage and polyadenylation specificity factor (CPSF)

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5
Q

_____ an RNA binding protein that binds the GU rich region of the 3’ end of eukaryotic mRNA

A

cleavage stimulation factor F (Cstf)

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6
Q

(T/F) the CA sequence at the 3’ end of mRNA is recognized by either CPSF or Cstf

A

false

recognized by another factor involved in cleavage of 3’ tail prior to poly A addition

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7
Q

(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

A

false

this is the second step

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8
Q

(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

A

true

this is the first step!

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9
Q

(T/F) Cleavage of 3’ end occurs and is the 3rd step in the initial mRNA 3’end processing

A

true

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10
Q

_____ the enzyme that adds about 200 A nucleotides onto 3’ end produced by the cleavage of 3’ end of mRNA

A

poly-A-polymerase

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11
Q

(T/F) Addition of poly-A

tail requires a template and encoded by a gene

A

false

does not require a template and thus is not encoded
by gene

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12
Q

(T/F) Poly-A-binding
proteins bind to poly-A
tail and remain attached as mRNA leaves nucleus

A

true

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13
Q

(T/F) Poly-A-binding

proteins assist in initiation phase of protein translation of the mRNA

A

true

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14
Q

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

A

none of the above. all are bound to mRNA`

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15
Q

(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

A

false

ACTIVELY transports it. the rest is true

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16
Q

____ the most abundant form of RNA in cells and form the core of ribosomes

A

rRNA

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17
Q

(T/F) prokaryotes and eukaryotes use one RNA Pol to synthesize all RNAs

A

false

only applies to bacteria
euks have specialized pols

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18
Q

(T/F) RNA Pol l is similar in structure to RNA Pol ll in all aspects

A

false

RNA pol 1 lacks a C terminal tail, lack a 5’ cap or poly A tail

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19
Q

____ eukaryotic RNA used specifically for production of rRNAs

A

RNA pol I

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20
Q

(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)

A

true

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21
Q

(T/F) one mRNA transcribed from a gene may be translated many times. the same is true for structural RNAs

A

false

true for mRNAs but rRNA must occur in abundance

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22
Q

(T/F) human cells contain about 200 rRNA gene

copies/haploid genome in small clusters spread over five different chromosomes

A

true

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23
Q

_____ are the four types of eukaryotic rRNAs that are each present as a single copy per ribosome

A

18S, 5.8S, 28S, and 5S

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24
Q

(T/F) 18S, 5.8S, and 28S rRNAs are derived from a single chemically modified mRNA

A

false

large 45S rRNA precursor

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25
Q

(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

A

false

uridine to pseudouridine

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26
Q

(T/F) 5S rRNA is transcribed from a different set of genes by RNA Pol lll and is not chemically modified

A

true

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27
Q

(T/F) snoRNAs complexed with proteins to snoRNPs direct modification and cleavage of 45S rRNA precursor

A

true

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28
Q

_____ 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

A

nucleolus

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29
Q

(T/F) the nucleolus is bound by a membrane

A

false

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30
Q

(T/F) U6 snRNP for splicesome and telomerase are produced in nucleus

A

false

in NUCLEOLUS

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31
Q

(T/F) Although rRNA genes occur in clusters on different chromosomes , the gene clusters are concentrated in nucleolus

A

true

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32
Q

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

A

C

transport out of NUCLEUS

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33
Q

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’

A

D

5’ to 3’

34
Q

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

A

B

this is false. codon is not ambiguous

1 aa = coded by one or more codons
but 1 codon = 1 aa

35
Q

____ describes the arrangement of the third base in a degenerate codon

A

wobble base

36
Q

*___ acts as initiation codon that is present at the start of all translated proteins and specifies the aa methionine

A

AUG codon

37
Q

(T/F) A mutation that alters the third base will not have any effect on the amino
acid at that position

A

true

coz codons are degenerate

38
Q

(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

A

false

“U” base. no T in mRNA
the rest is true

39
Q

*(T/F) one codon codes for more than one amino acid

A

false

genetic code is NOT ambiguous

40
Q

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

A

C

41
Q

(T/F) One mRNA sequence could generate three different amino acid
sequences that encodes actual protein sequence

A

false

only one reading frame encodes a protein

42
Q

____ are clover shaped molecules that act as adaptor molecules which literally match amino acids with their respective codons in mRNA (physically)

A

tRNAs

43
Q

(T/F) tRNAs fold into its shape thtough hydrogen bonding

A

false

intramolecular base pairing

44
Q

_____ set of three consecutive nucleotides in tRNA region that binds to complementary nucleotides in the codons of mRNA

A

Anticodon

45
Q

(T/F) A short region at the 3’ end of the tRNA is attached an amino acid that corresponds to the codon in mRNA

A

true

46
Q

____ and ___ are modified bases in tRNA

A

pseudouridine and

dihydrouridine

47
Q

____ polymerase that transcribes tRNA

A

RNA pol III

48
Q

(T/F) Some tRNA precursors in both prokaryotes and eukaryotes contain introns that are spliced

A

true

49
Q

(T/F) tRNA, like mRNA do not contain lariat formation and its reaction is catalyzed by proteins

A

false

applies to tRNA ONLY

50
Q

(T/F) About 10% of all nucleotides in ALL tRNA are modified version of either A, C, U, or G

A

true

51
Q

(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

A

false

this is COVALENT

52
Q

(T/F) humans have hundreds of tRNA genes that represents only about 48 anticodons

A

true

497 tRNA genes = 48 anticodon

53
Q

(T/F) wobble interactions or atypical covalent bonding enable a number of tRNAs are capable of pairing with several codons

A

false

wobble interaction is thru atypical hydrogen bonding

54
Q

(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

A

true

55
Q

*(T/F) 5’ base of tRNA

anticodon that pairs with 3’ base of mRNA codon

A

true

56
Q

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

A

inosine = A, C or U

no T in mRNA

57
Q

____ is formed when an aa is coupled to its appropriate tRNA

A

aminoacyl-tRNA

58
Q

(T/F) formation of aminoacyl-tRNA is the activation step in protein synthesis

A

true

59
Q

____ catalyzes the amino acid activation step in protein synthesis

A

aminoacyl-tRNA synthetase

60
Q

____ is formed when aa is coupled to AMP by aminoacyl-tRNA synthetase

A

aminoacyl-AMP

61
Q

(T/F) aminoacyl-tRNA is formed when aminoacyl moiety is transferred to tRNA

A

true

62
Q

*(T/F) Cells contain a different synthetase for each type of amino acid

A

true

20 of them!

63
Q

(T/F) overall coupling reaction requires hydrolysis of ATP

A

true

64
Q

____ the process where the aminoacyl is moved from 2’OH to 3’ OH of ribose in a aminoacyl tRNA synthetase reaction

A

transesterification

65
Q

______ the only tRNA is used in protein synthesis

A

3’-O aminoacyltRNA

66
Q

_____ & ____ are the essential adaptor molecules that convert nucleotide sequence into an amino acid sequence

A

aminoacyl-tRNA synthetase and aminoacyl-tRNA

and think about their function!

67
Q

(T/F) AminoacyltRNA

synthetases recognize specific binding sites on tRNA molecules and almost always involves the anticodon

A

false

anticodon is a component but not always involved. the rest is true

68
Q

(T/F) large amino acids have a high affinity to its Aminoacyl-tRNA
synthetase active site

A

false

larger =does not fit active site = lower affinity

69
Q

(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

A

false

correct aa = excluded
incorrect aa = enters pocket = removed from enzyme

70
Q

(T/F) a protein is synthesized from its N-terminal to its C-terminal

A

true

71
Q

(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

A

true

72
Q

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

A

D

large subunit does this

small subunit = scaffold for base pairing of tRNA and mRNA

73
Q

(T/F) Ribosomal subunits are only joined when synthesizing proteins

A

true

74
Q

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

A

B

2 amino acids/sec in eukaryotes
20 amino acids/sec in
prokaryotes

75
Q

(T/F) Ribosomes contain three RNA-binding sites but binds only two RNAs at a time

A

false

four binding sites, the rest is true

76
Q

_______ catalyzes the formation of a peptide bond between the amino acids in protein synthesis

A

peptidyl transferase

77
Q

(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

A

false

detached from P site, linked at the A site

78
Q

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

A

C

in the P site

79
Q

(T/F) viruses use the same genetic codes as humans and prokaryotes

A

False

Viruses are not organisms. But they use the same genetic code (? Clarify)

80
Q

(T/F) mRNA is read 5’-3’ direction

A

True

Biochem 2 (13 decks)

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