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biochemistry > biochem gene expression and protein synthesis > Flashcards

biochem gene expression and protein synthesis Flashcards

1
Q

is the turning on or activation of a gene

A
  • Gene expression
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2
Q

the process by which information encoded in a DNA molecule is copied into an mRNA molecule.

A
  • Transcription
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3
Q

starts when the DNA double helix begins to unwind near the gene to be transcribed.

A
  • Transcription
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4
Q

How many strand of the DNA is transcribed.

A

1

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5
Q

assemble along the unwound DNA strand in a complementary sequence.

A
  • Ribonucleotides
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6
Q
  • catalyze transcription: poly I for rRNA formation, poly II for mRNA formation, and poly III for tRNA formation.
A

polymerases

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7
Q
  • A eukaryotic gene has two parts
A

structural and regulatory genes

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8
Q

that is transcribed into RNA; the structural gene is made of exons and introns.

A

structural genes

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9
Q

genes that controls transcription; the regulatory gene is not transcribed but has control elements, one of which is the

A

regulatory genes

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10
Q

regulatory genes that controls transcription; the regulatory gene is not transcribed but has control elements, one of which is the

A

promoter

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11
Q
  • There is always a sequence of bases on the DNA strand ca led an
A

initiation signal

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12
Q

Promoters also contain

A

consensus sequences

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13
Q
  • Promoters also contain consensus sequences such as the
A

TATA box

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14
Q
  • A TATA box lies approximately __base pairs upstream (Figure 25.2).
A

26

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15
Q
  • A l three RNA polymerases interact with their promoter regions via _____ that are binding proteins.
A

transcription factors

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16
Q
  • After initiation, RNA polymerase zips up the complementary bases in a process ca led
A

elongation

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17
Q
  • Elongation is in the____ direction
A

5’ - 3’

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18
Q
  • At the end of each gene is a
A

termination sequence.

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19
Q
  • Poly II has two different forms
A
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20
Q
  • At its C-terminal domain, it has ___and ___repeats that can be phosphorylated
A

Ser and Thr

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21
Q
  • When poly II starts initiation, it is
A
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22
Q
  • At its C-terminal domain, it has Ser and Thr repeats that can be
A

phosphorylated

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23
Q
  • After termination of the transcription
A

it is dephosphorylated

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24
Q
  • After termination of the transcription, it is dephosphorylated by a
A

phosphatase.

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25
Q
  • In this manner, poly II is constantly recycled between its
A

initiation and elongation roles.

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26
Q
  • The RNA products of transcription are not necessarily functional RNAs. They are made functional by
A

post- transcription modification

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26
Q
  • The 5’ end acquires a
A

methylated guanine.

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26
Q
  • The RNA products of transcription are
A

not necessarily functional RNAs.

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27
Q
  • The 3’ end acquires a polyA tail that may contain from
A

100 to 200 adenine residues.

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28
Q
  • Functional rRNA also undergoes
A

post-transcription methylation.

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29
Q
  • mRNA, rRNA, and tRNA a l participate in
A

translation

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30
Q
  • Protein synthesis takes place on
A

ribosomes

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31
Q
  • A ribosome dissociates into
A

larger and a smaller body.

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31
Q
  • Together the 40S and 60S ribosomes form a unit on which
A

mRNA is stretched out.

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31
Q
  • In higher organisms, the larger body is called a ___ribosome; the smaller body is called a ____ ribosome
A

60S ribosome

40S ribosome

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32
Q
  • Triplets of bases on mRNA are called
A

codons

33
Q
  • Each tRNA is specific for
A

only one amino acid.

34
Q
  • Each ce l carries at least
A

20 specific enzymes

35
Q
  • Each cell carries at least 20 specific enzymes, each specific for
A

one amino acid.

36
Q
  • Each enzyme recognizes
A

only one tRNA.

37
Q
  • The enzyme bonds the activated amino acid to the 3’ terminal -OH group of the appropriate tRNA by an
A

ester bond.

38
Q
  • At the opposite end of the tRNA molecule is a
A

codon recognition site

39
Q
  • The codon recognition site is a sequence of three bases ca led an
A

anticodon

40
Q
  • By ____ the genetic code was broken.
A

1967,

41
Q
  • AUG also serves as an
A

initiation signal.

42
Q
  • Only __ and___ have one codon each.
A

Trp and Met

43
Q
  • 3 (UAA, UAG, and UGA) serve as
A

termination signals

44
Q
  • More than one triplet can code for the same amino acid; ___, __, and ___, for example, are each coded for by six triplets.
A

Leu, Ser, and Arg

45
Q
  • The code is almost universal: it the same in viruses, prokaryotes, and eukaryotes; the only exceptions are some
A

codons in mitochondria.

45
Q
  • There are four major stages in protein synthesis:
A
  • Activation
  • Initiation
  • Elongation
  • Termination
45
Q

is bound to its own particular tRNA by an ester bond between the carboxyl group of the amino acid and the 3’-OH of the tRNA.

A

activated amino acid

46
Q
  • For the 15 amino acids coded for by 2, 3, or 4 triplets, it is only the___ letter of the codon that varies
A

third

47
Q

the process whereby a base sequence of mRNA is used to create a protein.

A

translation

48
Q

amino acid activation

A
  • amino acids
  • tRNAs
  • aminoacyl-tRNA synthetases
  • ATP, Mg2+
49
Q

The aminoacyl-AMP remains bound to the enzyme and binding of the correct amino acid is verified by an editing site on the tRNA synthetase.

A

amino acid

50
Q

There are specific binding sites on tRNAs that are recognized by aminoacyl-tRNA synthetases.

A

tRNA

51
Q
  • Termination codons (____, ___, or ___) of mRNA.
A

(UAA, UAG, or UGA)

52
Q

the various methods used by organisms to control which genes

A

gene regulation

53
Q
  • In eukaryotes, transcription is regulated by three elements:
A

promoters, enhancers, and response elements.

54
Q

promoters are defined by an_____ and _____ such as TATA or GC boxes.

A

initiator and conserved sequences

55
Q

______find their targeted sites by twisting their protein chains so that a certain amino acid sequence is present at the surface.

A

Transcription factors

55
Q
  • Different ____ bind to different modules of the promoter.
A

transcription factors

56
Q

a low the rate of synthesis of mRNA

A
  • Transcription factors
57
Q
  • One such conformational twist is provided by
A

metal binding fingers

58
Q
  • Two other prominent transcription factor conformations are the___and the____
A

helix-turn-helix

leucine zipper

59
Q
  • Transcription factors also possess____ , which reduce the rate of transcription.
A

suppressors

60
Q

are activated by their transcription factors in response to an outside stimulus.

A

response elements

61
Q
  • During translation, Enzymes called ______catalyze this bonding
A

aminoacyl-tRNA synthase (AARS)

61
Q

may speed up transcription

A

enhancers

62
Q
  • The response element of steroids is in front of and about____base pairs upstream from the starting point of transcription.
A

250

62
Q
  • The stop codons must be recognized by
A

release factors

63
Q
  • The release factor combines with GTP and binds to the ribosomal A site when that site is occupied by the
A

termination codon.

64
Q
  • The stop codons must be recognized by
  • The release factor combines with GTP and binds to the ribosomal A site when that site is occupied by the termination codon.
A
  • Termination control
65
Q
  • In most proteins, the Met at the N-terminal end is removed by Met-aminopeptidase.
  • Certain proteins ca led help newly synthesized proteins to fold properly.
  • If rescue by chaperones fails, may degrade the misfolded protein.
A
  • Post-translational control
66
Q
  • In most proteins, the Met at the N-terminal end is removed by
A

Met-aminopeptidase.

67
Q

a heritable change in the base sequence of DNA.

A

mjtation

67
Q
  • If rescue by chaperones fails, _____ may degrade the misfolded protein.
A

proteasomes

67
Q
  • Certain proteins called ______ help newly synthesized proteins to fold properly
A

chaperones

68
Q
  • If the original codon is CAT, it may be transcribed onto mRNA as
A

GUC which codes for Val

68
Q
  • It is estimated that, on average, there is one copying error for every
A

1010 bases

69
Q
  • Base errors can also occur during
A

transcription in protein synthesis (a nonheritable error).

70
Q

a chemical that causes a base change in DNA.

A

mutagen

71
Q
  • Consider the mRNA codons for
A

Val, which are CAT, CAC, CAG, and CAA.

72
Q
  • Many changes in base sequence caused by radiation and mutagens do not become mutations because
    cells have repair mechanisms called
A

nucleotide excision repair

73
Q

DNA from two sources that have been combined into one molecule.

A

recombinant DNA

74
Q

recombinant DNA, One example of the technique begins with plasmids found in the cells of

A

Escherichia coli

75
Q

a small, circular, double-stranded DNA molecule of bacterial origin.

A

plasmid

76
Q
  • A class of enzymes called _____ cleave DNA at specific locations.
A

restriction endonucleases

77
Q
  • The human gene is now spliced into the plasmid by the enzyme
A

DNA ligase

biochemistry (19 decks)

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