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BIOCHEM LEC > TRANSLATION > Flashcards

TRANSLATION Flashcards

1
Q

the process of protein synthesis

A

translation

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2
Q
  • Synthesis of proteins in ribosomes
  • Uses mRNA as a template; and
  • tRNA as an adapter molecule carries the amino acids to the growing polypeptide chain
A

translation

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3
Q

TRANSLATION

uses ____ as template

A

mRNA

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4
Q

TRANSLATION

requires a ____

A

genetic code

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5
Q

TRANSLATION

Used to identify the specific amino acid sequence

A

genetic code

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6
Q

TRANSLATION

Any ____ in the nucleotide sequence may result in an incorrect amino acid being inserted into the protein -> disease or even death

A

alteration

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7
Q

The genetic code is a “____” that identifies the correspondence between a sequence of nucleotide bases and a sequence of amino acids.

A

dictionary

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8
Q

Each individual “word” in the code is composed of three nucleotide bases called

A

codons

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9
Q

STOP CODONS

A

UAG
UGA
UAA

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10
Q

There are a total of ____ codons

A

64

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11
Q

____ codons code for amino acids

A

61

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12
Q

____ stop codons that terminate translation

A

3

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13
Q

Start or initiating codon

A

AUG

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14
Q

Start or initiating codon (AUG) for EUKARYOTES

A

METHIONINE

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15
Q

Start or initiating codon (AUG) for PROKARYOTES

A

N-formylmethionine

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16
Q

CHARACTERISTICS OF THE GENETIC CODE

Multiple codons may code for the same amino acid

A

degenerate

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17
Q

CHARACTERISTICS OF THE GENETIC CODE

A specific codon always codes for the same amino acid

A

unambiguous

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18
Q

CHARACTERISTICS OF THE GENETIC CODE

The codons are read in a continuing sequence of nucleotide triplets until a translation codon is reached

A

nonoverlapping

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19
Q

CHARACTERISTICS OF THE GENETIC CODE

It has been conserved from very early stages of evolution with only slight differences in the manner in which the code is translated

A

universal

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20
Q

COMPONENTS REQUIRED FOR TRANSLATION

All the ____ that eventually appear in the finished protein must be present at the time of protein synthesis. If one ____ is missing, translation stops at the codon specifying that ____

A

AMINO ACID

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21
Q

COMPONENTS REQUIRED FOR TRANSLATION

at least 50 tRNA species

A

HUMANS

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22
Q

COMPONENTS REQUIRED FOR TRANSLATION

at least 30 tRNA species

A

BACTERIA

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23
Q

COMPONENTS REQUIRED FOR TRANSLATION

The carboxyl group of the amino acid is in an ____ with the 3′-hydroxyl of the ribose portion of the A nucleotide in the –CCA sequence at the 3′-end of the tRNA.

A

ESTER LINKAGE

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24
Q
  • a 3-base nucleotide sequence which pairs with a specific codon on the mRNA
  • This codon specifies the insertion into the growing polypeptide chain of the amino acid carried by that tRNA.
A

ANTICODON

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25
Q
  • Required for the attachment of amino acids to their corresponding tRNA
  • Covalent attachment of the alpha-carboxyl group of an amino acid to the A in the –CCA sequence at the 3’ end of its corresponding tRNA
A

aminoacyl-tRNA sequence

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26
Q

are large complexes of protein and ribosomal RNA (rRNA), in which rRNA predominates

A

ribosomes

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27
Q

RIBOSOMES

prokaryotes

A

50S & 30S

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28
Q

RIBOSOMES

eukaryotes

A

60S and 40S

29
Q

S means

30
Q

determines the accuracy of translation by insuring correct base-pairing between the mRNA codon and the tRNA anticodon

A

small ribosomal subunit

31
Q

catalyzes formation of the peptide bonds that link amino acid residues in a protein

A

large ribosomal unit

32
Q
  • binds an incoming aminoacyl-tRNA as directed by the codon currently occupying this site.
  • This codon specifies the next amino acid to be added to the growing peptide chain.
33
Q

occupied by peptidyl-tRNA (tRNA that carries the chain of amino acids that has already been synthesized)

34
Q

occupied by the empty tRNA as it is about to exit the ribosome

35
Q

Codon Recognition by the tRNA

follows the rules of ____ and ____ binding, that is, the mRNA codon is read 5′→3′ by an anticodon pairing in the opposite (3′→5′) orientation

A

complementary and antiparallel binding

36
Q

STEPS IN TRANSLATION

A

initiation
elongation
termination

37
Q
  • Assembly of the components of translation
  • Two ribosomal subunits
  • mRNA
  • Before initiation, aminoacyl-tRNA synthetases attach amino acids to their respective tRNAs (charging)
  • Requires hydrolysis of ATP -> AMP
  • Proofreading is possible to remove incorrect amino acids
  • Initiation factors (IF-1, IF-2, IF-3, eIF)
  • GTP (and ATP for eukaryotes)
A

initiation

38
Q

INITIATION

In eukaryotes, the ____ binds close to the cap structure at the 5’-end of the mRNA and moves 5’ - 3’ along the mRNA until it encounters the initiation codon (AUG).

A

small (40s) ribosomal unit

39
Q

INITIATION

Initiation codon is recognized by a

A

special initiator tRNA

40
Q

INITIATION

In both prokaryotic and eukaryotic cells, this N-terminal Met is usually ____ before translation is completed

41
Q
  • A cyclic process on the ribosome in which one amino acid at a time is added to the growing peptide chain
  • Requires elongation factors
  • Steps:
    1. Binding of aminoacyl tRNA to the A site
    2. Peptide bond formation catalyzed by peptidyl transferase
    3. Translocation of the ribosome on the mRNA
    4. Expulsion of the deacylated tRNA from the P- and E-sites
A

ELONGATION

42
Q
  • Occurs when one of the three termination codons moves into the A site
  • Results in the release of the newly synthesized protein and dissociation of the ribosomes and mRNA
A

termination

43
Q
  • In most cases, accurate base pairing is required only in the first two nucleotide positions of an mRNA codon
  • Allows a single tRNA to recognize more than one codon
A

tRNA wobble hypothesis

44
Q

Addition of a single amino acid to the polypeptide chain requires cleavage of four high-energy bonds from ATP and GTP:
* tRNA aminoacylation: ATP -> AMP
* Loading tRNA onto ribosome: GTP -> GDP
* Translocation: GTP -> GDP

A

energy requirement

45
Q

tRNA aminoacylation

A

ATP -> AMP

46
Q

Loading tRNA onto ribosome

A

GTP -> GDP

47
Q

Translocation

A

GTP -> GDP

48
Q

Post-translational Modifications

A

Removal of excess amino acids
Phosphorylation
Glycosylation
Hydroxylation
Proteins that are defective or destined for rapid turnover are marked for destruction by ubiquitin and degraded by proteasomes

49
Q

Proteins that are defective or destined for rapid turnover are marked for destruction by ____ and degraded by proteasomes

50
Q
  • Amanita phalloides (death cap)
  • Alpha-amanitin -> inhibits RNA polymerase II
  • Presents with GI symptoms, acute liver failure, and may be fatal
A

amanita mushroom poisoning

51
Q

AMANITA MUSHROOM POISONING

inhibits RNA pol II

A

alpha-amanitin

52
Q

AMANITA MUSHROOM POISONING

also known as death cap

A

amanita phalloides

53
Q
  • Exotoxin of Corynebacterium diphtheriae
  • Inactivates the eukaryotic elongation factor EF-2, preventing translocation
  • Results in local tissue destruction and pseudomembrane formation
A

diphtheria toxin

54
Q

binds to the BETA subunit of prokaryotic RNA pol (selectively toxic) -> prevents chain growth beyond 3 nucleotides
Antitubercular drug

A

rifampicin

55
Q
  • Antineoplastic
  • Intercalates between the DNA bases and inhibits transcription initiation and elongation
A

dactinomycin
(actinomycin D|)

56
Q

Bind to 30s subunit and interferes with initiation

A

streptomycin
aminoglycosides

57
Q

Prevents binding of aminoacyl-tRNA to the A site

A

tetracycline

58
Q

Inhibits prokaryotic peptidyltransferase

A

chloramphenicol

59
Q

Bind to the 50S and inhibits translocation

A

clindamycin
macrolides

60
Q
  • Any permanent heritable change in the DNA base sequence of an organism
  • Has the potential to change the base sequence of mRNA and the amino acid sequence of proteins
61
Q

POINT MUTATION

purine-purine or pyrimidine-pyrimidine

A

TRANSITION

62
Q

POINT MUTATION

purine-pyrimidine or pyrimidine-purine

A

TRANSVERSION

63
Q

POINT MUTATION

  • New codon codes for same amino acid
  • No effect on protein
A

SILENT MUTATION

64
Q

POINT MUTATION

  • New codon codes for different amino acid
  • Variable effects on protein
A

MISSENSE MUTATION

65
Q

POINT MUTATION

  • New codon is a stop codon
  • Shorter than normal, usually non-functional protein
A

NONSENSE MUTATION

66
Q
  • Deletion or addition of bases that should not be multiples of three
  • Shorter than normal, usually non-functional protein
A

FRAME SHIFT MUTATION

67
Q
  • Loss of large areas of chromosomes during unequal cross over in meiosis
  • Loss of function
  • Protein shorter than normal or entirely missing
A

LARGE SEGMENT DELETION

68
Q
  • Splice site is lost
  • Variable effects ranging from addition or deletion of a few amino acids to deletion of an entire exon
  • Examples:
    - Tay-Sachs, Gaucher, Beta-thalassemia
A

SPLICE DONOR OR ACCEPTOR

69
Q
  • Expansions in coding regions cause protein product to be longer than normal and unstable
  • Diseases often show anticipation in pedigree
  • Examples:
    * Huntington Disease
    * Fragile X Syndrome
    * Myotonic Dystrophy
A

THIRD REPEAT EXPANSION

BIOCHEM LEC (33 decks)

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