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BMSC 220 > Lecture #18 > Flashcards

Lecture #18 Flashcards

1
Q

A eukaryotic cell may contain millions of ________

A

ribosomes

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2
Q

More than 80% of the RNA in most cells consists of ______

A

rRNA

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3
Q

rDNA gene clusters gathered into _______. The bulk of a nucleolus is composed of ______ ribosomal subunits.

A

nucleolus, nascent

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4
Q

The Svedberg (S) unit offers a measure of a particle’s _____ indirectly based on its sedimentation rate under acceleration (i.e. how fast a particle of given size and shape settles to the bottom of a solution)

A

size

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5
Q

Few differences in the ______ and _____ of rRNA and protein components in bacterial and eukaryotic ribosomes

A

number, size

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6
Q

Both bacterial and eukaryotic ribosomes have nearly the same _______ and they function _____

A

structure, similarly

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7
Q

The 120 nt 5S rRNA is synthesized by RNAPol-____

A

III

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8
Q

The 45S precursor (around 13,000 nt) is synthesized by RNA pol ___. It is cleaved to 28S, 18S and 5.8S rRNA

A

I

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9
Q

___ ‘cut’ locations. First cut at site __ and __. Then, cut at site __ or __.

A

5, 1, 5, 2, 3

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10
Q

The 45S pre-RNA is processed _____-transcriptionally

A

post

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11
Q

A large number of ribonucleotides are modified to ribose-_______ forms (@100 residues) or enzymatically modified to ______ (@ 90 residues). All of the modified residues are found in the final gene products

A

methylated, pseudouridine

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12
Q

The processing is carried out by ______ (small nucleolar ribonucleoprotein particles, snoRNAs+proteins) that begin to associate with the primary transcript ______ transcription is completed

A

snoRNPs, before

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13
Q

There are about 200 different snoRNAs, ___ for every site in the pre-RNA that is ribose-methylated or converted uridine to pseudouridine

A

one

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14
Q

The positions of modified ribonucleotides with rRNAs are ________ in evolution

A

conserved

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15
Q

_____, 5’-CUGA-3’, is present in all snoRNAs that guide ribose methylation

A

BoxD

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16
Q

Site of __________ is in a fixed spot relative to a hairpin fold on snoRNA. The ____ sequence is conserved in snoRNAs that guide pseudouridylation.

A

pseudouridylation, ACA

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17
Q

________ RNAs are synthesized from genes that are found in small clusters (tDNA) scattered around the genome

A

Transfer

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18
Q

tRNAs are transcribed by RNA polymerase ____, and the primary transcript is trimmed on its 5’ and 3’ sides

A

III

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19
Q

The _________ ribonuclease P, involved in pre-tRNA processing, is present in bacterial and eukaryotic cells and consists of RNA and protein subunits

A

endonuclease

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20
Q

Information stored in a gene is present in the form of a genetic ____

A

code

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21
Q

Each amino acid in a polypeptide is encoded by three sequential nucleotides (nucleotide triplets), and the code words for amino acids were called _____

A

codons

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22
Q

Because DNA consists of four different bases, and there are _____ bases in a codon, 4 * 4 * 4 = 64

A

three

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23
Q

64 codons but only 20 amino acids. The genetic code is called degenerate or _________

A

redundant

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24
Q

A single amino acid may be coded by more than one ______

A

codon

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25
Q

To identify the codons, the codon assignment was determined by ________ of artificial mRNAs

A

transcription

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26
Q

The genetic code is considered to be _______, present in all organisms

A

universal

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27
Q

The first two codon bases for a particular amino acid are ______, whereas the third base may ____

A

invariant, vary

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28
Q

There are 64 codons for 20 amino acids and are read in the __-__ sense.

A

5’, 3’

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29
Q

The _____ codon encodes for Methionine (Met-M), and is always the ______ signal of translation

A

AUG, starting

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30
Q

There is 3 codons that stop the translation, ?

A

UAA, UGA and UAG.

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31
Q

What are the 5 kinds of mutations?

A

Silent (synonymous)
Nonsense (nonsynonymous)
Missense (nonsynonymous)
Frameshift
Splice Site

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32
Q

What are the 2 kinds of missense mutations?

A

Conservative
Non-conservative

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33
Q

_________ mutation: an amino-acid specifying codon is replaced by a codon for a different amino acid

A

Missense

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34
Q

_____-_____ mutation: an amino-acid specifying codon is replaced by a premature stop codon

A

stop-gain

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35
Q

_______ mutation: where the nucleotide substitution results in a new codon, but that codon codes for the same amino acid

A

Silent

36
Q

_____-_____ mutation: a natural stop codon is replaced by an amino acid-specifying codon

A

stop-loss

37
Q

________ mutation: mutation that introduces a stop codon into the genetic code and prevents the protein from being made completely

A

Nonsense

38
Q

A _________ missense mutation occurs when an amino acid is replaced with a similar one; a __________ missense mutations replaces the amino acid with another belonging to a different class

A

conservative, Non-conservative

39
Q

________ mutation: would shift the reading frame

A

Frameshift

40
Q

_____ ____ mutation: which include mutations where a splice site is lost or gained, can lead to altered sequence f the downstream product

A

Splice Site

41
Q

Decoding the information in an mRNA is accomplished by _______, which act as adaptors

A

tRNAs

42
Q

All tRNAs are roughly the same _____ and _____; and all mature tRNAs have the triplet sequence ____ at their 3’ end.

A

length, shape, CCA

43
Q

tRNA properties:
Contains modified _______ – posttranslational process.
________ intra chain base-pairing.

A

nucleotides, Complementary

44
Q

tRNA structure appears as a _______ as drawn in 2D

A

cloverleaf

45
Q

Different tRNAs have similar L-shaped 3-D structures that allow them to be recognized by amino-acyl-synthetases which attach the appropriate _____ ____

A

amino acid

46
Q

All mature tRNAs have the sequence C-C-A- at ___ end that in eukaryotes are added post-transcriptionally by an enzyme

A

3’

47
Q

____________ of the base of the third position led Francis Crick to propose that the same tRNA may be able to recognize more than one codon (wobble hypothesis)

A

Interchangeability

48
Q

A ______ base pair is a pairing between 2 nucleotides in RNA that does not follow the Watson-Crick base pair rules

A

wobble

49
Q

The _______ interaction: The nucleotide at the 5’ end of the tRNA anticodon is capable of pairing with more than one nucleotide at the 3’ end (third position) of the mRNA codon

A

wobble

50
Q

tRNA charging: _____ requiring process to add amino acids to each tRNA; aminoacyl-tRNA synthetases _____ to each amino acid; __-step reaction; ________ capability.

A

energy, unique, 2, proofreading

51
Q

Protein synthesis (_______) is the most complex activity of the cell and the process is remarkably similar between prokaryotes and eukaryotes

A

translation

52
Q

The _____ subunit (“40S” in eukaryotes) the genetic message, and the ______ subunit (“60S” in eukaryotes) catalyzes peptide bond formation.

A

small, large

53
Q

The initiator tRNA-Met complex is loaded into the _____ subunit of the ribosome

A

small

54
Q

Eukaryotic cells require at least __ initiation factors comprising a total of more than __ polypeptide chains

A

12, 25

55
Q

Once the 43S preinitiation complex is formed, it is ready to find the __ mRNA. The ______ subunit moves 5’ to 3’ along the mRNA to find the first AUG.

A

5’, small

56
Q

The initiation factor dissociate, allowing the large ribosomal subunit to assemble with the complex and complete the ______

A

ribosome

57
Q

____ distinct complexes are formed during eukaryotic initiation

A

Two

58
Q

Ribosomes undergo a repetitive cycle of mechanical changes that is driven with energy released by GTP _______

A

hydrolysis

59
Q

Information stored in the mRNA determines the sequence of aminoacyl-tRNAs that the ribosome accepts during _______

A

translation

60
Q

________ RNAs play major roles in selecting tRNAs and ensuring accurate translation

A

Ribosomal

61
Q

There are three places on the ribosome where tRNAs bind: ?

A

the A, P, and E site

62
Q

___ site: binds to the incoming aminoacyl site carrying the new aa.

A

A (aminoacyl)

63
Q

__ site: holds the tRNA with the protein

A

P (peptidyl)

64
Q

__ site: holds the tRNA without the aa which is then released by the ribosome

A

E (exit)

65
Q

Elongation Step 1: ?

A

Aminoacyl-tRNA Selection

66
Q

Binding of the second aminoacyl-tRNA to the __ site requires the GTPase, elongation factor EF-Tu (or Tu) bacteria, eEF1A in eukaryotes

A

A

67
Q

Once bound to the mRNA codon, the GTP is ________ and the EF-Tu-GDP complex released, leaving the newly arrived aa-tRNA situated in the ribosome’s A site

A

hydrolyzed

68
Q

Elongation Step 2: ?

A

Peptide Bond Formation

69
Q

The second step in the elongation cycle is for a _______ _____ to form between two amino acids

A

peptide bond

70
Q

Peptide bond formation occurs _________ without the input of external energy. Catalyzed by peptidyl transferase (part of the large subunit)

A

spontaneously

71
Q

tRNA in __ site has no aa anymore while the tRNA in __ site has two

A

P, A

72
Q

A ribosome can catalyze the incorporation of approximately ____ amino acids into a growing polypeptide per second

A

ten

73
Q

Elongation Step 3: _________

A

Translocation

74
Q

The binding of EF-G (elongation factor) and the hydrolysis of its associated GTP results in the _______ of the ribosome relative to the mRNA. EF-G prokaryotes, EF-2 in eukaryotes

A

translocation

75
Q

As a result of this motion, the ribosome moves three ________ (1 codon) along the mRNA in the 5’ to 3’ direction

A

nucleotides

76
Q

Elongation Step 4: ?

A

Releasing the Deacylated tRNA

77
Q

The deacylated tRNA leaves the ribosome, emptying the __ site. For each cycle of elongation, at least ____ molecules of GTP are hydrolyzed.

A

E, two

78
Q

Each tRNA steps through _____ positions on the ribosome

A

three

79
Q

Some of the most destructive mutations are ones in which a single base pair is either _____ to or _______ from the DNA

A

added, deleted

80
Q

_________ mutations lead to the assembly of an entirely abnormal sequence of amino acids from the point of the mutation

A

Frameshift

81
Q

_________ occurs at one of the three stop codons: UAA, UAG, or UGA; requires release factors, which recognize stop codons. The final step is the ________ of the mRNA from the ribosome and the _________ of the ribosome.

A

Termination, dissociation, disassembly

82
Q

_______ mutations are responsible for roughly 30 % of inherited disorders in humans. Premature termination codons are also commonly introduced into mRNAs during splicing

A

Nonsense

83
Q

Cells possess an mRNA surveillance mechanism capable of detecting messages with premature termination codons called ?

A

non-sense-mediated decay (NMD)

84
Q

____ protects the cell from producing nonfunctional, shortened proteins

A

NMD

85
Q

A _________ (or polysome) is a complex of multiple ribosomes on mRNA, allowing simultaneous translation

A

polyribosome

86
Q

___________ increase the rate of protein synthesis

A

Polyribosomes

BMSC 220 (22 decks)

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