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Kaplan Biochemistry > Ch. 7: RNA and the Genetic Code > Flashcards

Ch. 7: RNA and the Genetic Code Flashcards

1
Q

central dogma of molecular biology

A

DNA (reverse) transcription RNA —> translation —> protein

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2
Q

how is mRNA made

A

transcribed from the template DNA strand by RNA polymerase then derived from from post transcriptional modifications to hnRNA

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3
Q

what does mRNA do

A

carries info specifying the amino acid sequence of the protein to the ribosome

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4
Q

codon

A

three - nucleotide segment that codes for proteins

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5
Q

how is mRNA monocistronic?

A

each molecule translates into only one protein product

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6
Q

what does tRNA do

A

recognizes and pairs with appropriate codon on an mRNA molecule while in the ribosome

forms high energy bonds needed to create peptide bonds in translation

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7
Q

where is rRNA made

A

in the nucleolus

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8
Q

what does rRNA do

A

catalyzes the formation of peptide bonds

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9
Q

anticodon

A

sequence on tRNA complementary to a codon on mRNA that allows the tRNA and mRNA to pair

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10
Q

how is condon/anticodon pairing oriented

A

antiparallel

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11
Q

what is the eukaryotic start codon

A

AUG (methionine)

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12
Q

what are the three stop codons

A

UAA (you are away)
UGA (you go away)
UAG (you are gone)

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13
Q

how is the genetic code degenerate

A

more than one codon can code for the same amino acid

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14
Q

wobble position

A

the third nucleotide in a codon that usually varies for amino acids with multiple codons

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15
Q

where do silent or degenerate mutations usually occur

A

the wobble position

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16
Q

what is a silent/degenerate mutation

A

a mutation that has no effect on the amino acid that is expressed

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17
Q

what is a point mutation

A

a mutation that effects one nucleotide

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18
Q

what are expressed mutations

A

mutation that effect the expression of an amino acid sequence

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19
Q

what is a missense mutation

A

mutation that substitutes the amino acid that was originally coded for

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20
Q

what is a nonsense mutation

A

mutation that codes for a stop codon where there wasn’t one originally

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21
Q

reading frame

A

three nucleotides of a codon

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22
Q

what is a frameshift mutation

A

some nucleotides are added or deleted, causing a shift in the reading frame

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23
Q

what occurs during transcription (big picture)

A

creation of mRNA from a DNA template

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24
Q

how is the coding strand similar to mRNA

A

identical except for T/U switch

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25
Q

how is the template strand similar to mRNA

A

complementary and antiparallel

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26
Q

what occurs during translation (step by step)

A
  • DNA unwinds via helicase and topoisomerase
  • RNA polymerase identifies the promoter region, binds to the TATA box with the help of transcription factors, and synthesizes RNA
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27
Q

what does RNA polymerase do

A

locates genes by searching for promoter regions and synthesizes RNA

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28
Q

what are promoter regions

A

specialized areas of DNA

29
Q

TATA box

A

RNA polymerase binding site at the ‘beginning’ of the promoter region

30
Q

what do transcription factors do

A

help RNA polymerase and to the TATA box/promoter region

31
Q

In what direction is mRNA constructed

A

5’ –> 3’ as RNA polymerase moves 3’ –> 5’

32
Q

what is the primary product of transcription

A

heterogenous nuclear RNA (hnRNA)

modified –> mRNA

33
Q

what structure carries out splicing

A

the spliceosome

34
Q

what are introns

A

noncoding sequences that are removed from the hnRNA in the form of a lariat

35
Q

what are exons

A

coding sequences that are ligated together in the hnRNA

36
Q

what is the 5’ cap

A

7-methylguanylate triphosphate cap added to the 5’ end of hnRNA during transcription that protects the mRNA from degradation in the cytoplasm

37
Q

what is the 3’ poly A tail

A

polyadenosyl tails that is added to the 3’ end of the mRNA and protects the sequence from rapid degradation

like a time-bomb fuse

38
Q

when has hnRNA matured into mRNA

A

when exons are ligated and the 5’ cap and 3’ tail are added

39
Q

what is the product of alternative splicing

A

multiple variants of proteins created from different combinations of exons from the same original gene

40
Q

how does the mRNA transcript exit the nucleus

A

nuclear pores

41
Q

where does translation occur

A

in the cytoplasm and in the ribosome

42
Q

what are the three stages of translation

A
  1. initiation
  2. elongation
  3. termination
43
Q

what occurs during initiation

A
  • small subunits bind to the 5’ cap
  • initiator tRNA ends to the start codon
  • large subunit binds to the small subunit
  • assisted by initiation factors
44
Q

what occurs in elongation

A

ribosome moves in the 5’ to 3’ direction, binding to sites A–> P –> E and synthesizing the protein

45
Q

what occurs at the A site

A

holds the new aminoacyl-tRNA which will be added to the growing chain

46
Q

what occurs at the P site

A

holds the tRNA that carries the growing chain

47
Q

what occurs at the E site

A

uncharged tRNA pauses before exiting ribosome

48
Q

what occurs during termination

A
  • stop codons move into the A site
  • release factor binds to codon, causing H2O to be added
  • H2O causes termination factors to hydrolyzed polypeptide chain and dissociate subunits
49
Q

what to chaperones do

A

assist in the protein folding process

50
Q

phosphorylation

A

addition of phosphate group by protein kinases to activate or deactivate proteins

51
Q

carboxyation

A

addition of carboxylic acid groups to serve as calcium binding sites

52
Q

glycosylation

A

addition of ogliosaccharaides to determine cellular destination

53
Q

prenylaton

A

addition of lipid groups

54
Q

operon

A

cuter of genes transcribed as a single mRNA

55
Q

structural gene

A

codes for the protein of interest

56
Q

operator site

A
  • upstream of structural gene
  • nonstranscribable
  • capable of binding repressor protein
57
Q

promoter site

A
  • upstream of operator site

- provides place for RNA polymerase to bind

58
Q

regulator ene

A
  • furthest upstream

- codes for repressor protein

59
Q

how do repressors act in inducible systems

A

bind to operator site and act as a roadblock to transcribing the structural gene

unbind in the presence of an inducer

60
Q

negative control mechanisms

A

binding of protein reduces transcriptional activity

61
Q

how is a repressor removed in an inducible system

A

inducer binds to repressor so that repressor cannot bind to promoter site

62
Q

positive control mechanisms

A

binding of a molecule increases transcription of a gene

63
Q

how do repressors act in repressible systems

A

inactive until it binds with a corepressor, then binds to operator site

64
Q

what are transcription factors

A

transcription-activating proteins that search the DNA looking for specific binding motifs

65
Q

DNA binding domain of a transcription factor

A

binds to a specific nucleotide sequence in the promoter region

66
Q

Activation domain of the transcription factor

A

allows for the binding of several transcription factors

67
Q

enhancers

A

group of response elements that allows for the control of gene’s expression by multiple signals

variety of signals can increase transcription –> transcription more likely

68
Q

how does acetylation affect chromatin structure

A

opens chromatin conformation, allows for increased transcription

69
Q

how does DNA methylation affect chromatin structure

A

silences genes by attaching methyl groups which prevent transcription

Kaplan Biochemistry (9 decks)

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