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Foundations 110 > Lecture 4 > Flashcards

Lecture 4 Flashcards

1
Q

genetic code is – with very few exceptions (e.g. mitochondria) the same codons specify the same amino acids in all organisms.

A

universal

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2
Q

genetic code is – as there are 61 triplets coding for only 20 amino acids, so more than one codon can specify the same amino acid.

A

degenerate or redundant

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3
Q

genetic code is – as each codon specifies only one aa

A

unambiguous

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4
Q

genetic code is almost always read –

A

linearly and continuously

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5
Q

The linear order of codons specifying the order of amino acids in a protein is referred to as the –

A

reading frame

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6
Q

Synthesis of all proteins in eukaryotic and prokaryotic cells begins with methionine. The codon specifying this methionine is the Start codon and is usually –

A

AUG

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7
Q

The reading frame proceeds continuously as triplets to the –

A

STOP codon.

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8
Q

Mutations in the DNA can alter the coding sequence either directly or by–

A

affecting splicing

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9
Q

mutations that alter coding sequence can cause inherited or – (e.g. cancer) disease.

A

spontaneous

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10
Q

TTT to TTC mutation in DNA results in UUU to UUC codon change in mRNA but both encode phenylalanine so the protein would be the same.

A

silent mutation

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11
Q

a change from GAA to GTA in the b-globin gene results in the 6th codon specifying valine (GUA) instead of glutamate (GAA). This mutation causes sickle cell disease

A

missense mutation

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12
Q

TTG to TAG change in the DNA results in UUG (leucine) to UAG (STOP).

A

nonsense mutation

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13
Q

nonsense mutation – the protein

A

shortens

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14
Q

Insertion or deletion, in-frame: insertions or deletions of multiples of 3 nucleotides will result –

A

in addition or deletion of amino acids

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15
Q

most common deletion in frame causes –

A

cystic fibrosis

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16
Q

deletion of the codon specifying the phenylalanine at position 508. AT[C TT]T GGT to ATT GTT in DNA results in AUC UUU GGU (ile phe gly) to AUU GGU (ile gly)

A

deletion, in frame

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17
Q

Frameshift: insertion or deletion of nucleotides not divisible by 3 changes the reading frame – of the mutation

A

downstream

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18
Q

TTG GAA TTT to TTG [C]GA ATT T in DNA results in UUG GAA UUU (leu glu phe…) to UUG CGA AUU U (leu arg ile…)

A

frameshift

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19
Q

encodes the amino acid sequence

A

mRNA

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20
Q

tRNA serves as the – that matches the appropriate amino acid to a codon

A

adaptor (translator)

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21
Q

rRNA is a key structural component of ribosomes and –

A

catalyzes formation of the peptide bond

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22
Q

Translation also requires amino acids, ribosomal proteins, –, and other protein factors.

A

energy in the form of ATP and GTP

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23
Q

The mRNA contains several elements particularly important for translation – the START codon, the coding region, and the STOP codon.

A

the 5’ cap,

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24
Q

Although distinct in –, all tRNAs have common structural characteristics:

A

sequence

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25
Q

tRNAs: – at the 3’ end where the amino acid attaches in a high energy bond.

A

CCA sequence

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26
Q

tRNAs: An – containing a 3 nucleotide anticodon that base-pairs with the cognate codon in mRNA

A

anticodon loop

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27
Q

T/F: tRNAs have many bases other than A, C, U and G.

A

true

28
Q

tRNAs: An L-shaped 3-dimensional structure formed by –.

A

RNA double helices

29
Q

– “charge” tRNAs with amino acids

A

Aminoacyl tRNA synthetases

30
Q

charging tRNA with aa is a 2 step process that requires –

A

ATP

31
Q

In the first step of charging a tRNA, the tRNA synthetase uses ATP to catalyze addition of – of an amino acid to form the high energy intermediate aminoacyl-AMP.

A

AMP to the a-carboxy group

32
Q

in the second step of charing a tRNA, he amino acid is transferred to the – of the tRNA to generate aminoacyl-tRNA

A

3’ or 2’ OH

33
Q

Each tRNA synthetase is specific for one amino acid and –

A

one or a few tRNAs.

34
Q

Some tRNA synthetases have proof-reading mechanisms for –amino acids from tRNA. Mistakes occur about once every 104 to 105 reactions.

A

removing incorrect

35
Q

Charged tRNA recognizes the appropriate codon in mRNA because the anti-codon is – to the codon specifying the amino acid carried by that tRNA

A

complementary

36
Q

Anti-codon and codon interact through–

A

base-pairing

37
Q

Interaction of codons and anticodons follows the normal base-pairing rules (A:U, G:C) in the first 2 nucleotides of the codon but has – in the third position

A

“wobble”

38
Q

wobble in 3rd position allows – of the code so that a single tRNA can base-pair with multiple codons specifying an amino acid.

A

degeneracy

39
Q

– are the translation machine

A

Ribosomes

40
Q

T/F: Ribosomes of eukaryotes and prokaryotes are similar but not identical

A

true

41
Q

Mitochondrial ribosomes are more closely related to – ribosomes

A

bacterial

42
Q

All ribosomes are – made up of 2 subunits, one small and one large.

A

ribonucleoprotein particles (both RNA and proteins)

43
Q

Translation proceeds in the 5’ to 3’ direction on mRNA and synthesizes proteins from the –

A

amino-terminus to the carboxy-terminus

44
Q

GTP hydrolyzing proteins which cycle between active and inactive states

A

GTPases

45
Q

GTP hydrolysis is –, providing time for the active form to function

A

slow

46
Q

The protein assumes a different – in the two states, providing a molecular switch that can control a process or pathway

A

3-dimensional conformation

47
Q

GTPase switches are called –

A

G protein

48
Q

Initiation involves association of tRNAi-Met, mRNA and the small (40S) subunit so that tRNAi-Met base-pairs with the –

A

Start codon

49
Q

after the tRNAi-Met base pairs with the start codon, the – associates to generate translationally competent complex

A

large subunit

50
Q

Initiation is regulated by other proteins called –

A

initiation factors (eIF)

51
Q

tRNAi is a special tRNA for initiation – it is specific for methionine, is recognized by eIF and uniquely binds to the – in the ribosome

A

P site

52
Q

tRNAimet binding to 40S subunit regulated by –

A

GTPase switch protein

53
Q

– brings mRNA to 40S subunit

A

Cap-binding factor

54
Q

Cap-binding factor binds to 5’ cap of mRNA and brings mRNA to the tRNAi-Met/40s complex which then scans for –

A

AUG

55
Q

When tRNAi-met base-pairs with AUG then GTP is – and 60S large subunit associates.

A

hydrolyzed

56
Q

Elongation involves entry of a new aa-tRNA, peptide bond formation, and – of the ribosome to the next codon. Involves elongation factors.

A

translocation

57
Q

– base-pairs with 2nd codon, regulated by GTPase switch

A

aa2-tRNA

58
Q

Peptide bond formation catalyzed by –

A

28S RNA. (ribozyme)

59
Q

Elongation: – translocates along mRNA to bring 3rd codon into place for next aa-tRNa

A

Ribosome

60
Q

Termination involves recognition of the STOP codon, – from the tRNA, and dissociation of the mRNA and ribosomal subunits

A

cleavage of the polypeptide

61
Q

– are proteins that bind to STOP codon

A

Release factors

62
Q

Peptide is released by – activity of 28S rRNA

A

peptidyl transferase

63
Q

Termination: Dissociation of tRNA, – and ribosomal subunits.

A

mRNA

64
Q

Multiple individual ribosomes can translate mRNA at the same time, increasing the efficiency of translation.

A

polysomes

65
Q

Inhibitors of translation cause – .

A

cell death

66
Q

Since bacterial and eukaryotic ribosomes are distinct, bacterial ribosome inhibitors can be useful –

A

antibiotics

Foundations 110 (10 decks)

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