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Genetics 1 > Topic 2: Genetic Code and Mutation > Flashcards

Topic 2: Genetic Code and Mutation Flashcards

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1
Q

____: adenine and guanine

A

purines

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2
Q

____: cytosine, thymine, uracil

A

pyrimidines

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3
Q

each strand of DNA is composed of ____ and _____

A

nucleotides and sugar-phosphate backbone

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4
Q

where does the phosphodiester bond occur in DNA? between what two ends?

A

the 5’ phosphate group of a nucleotide and the 3’ hydroxyl group of the adjacent nucleotide

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5
Q

bases are _______

A

hydrophobic

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6
Q

the complementary strand runs _____ to the main strand

A

anti-parallel

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7
Q

__________: the theory that each new DNA duplex has one parental strand and one daughter strand

A

semi-conservative replication

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8
Q

purine nucleotides are _____-ringed

A

double

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9
Q

pyrimidine nucleotides are _____-ringed

A

single

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10
Q

how many base pairs twist with each turn of the double-helix?

A

10 base pairs/turn

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11
Q

the proportion of each base pairing is ______

A

equal (30% A = 30% T)

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12
Q

DNA replication is _____, forming a replication bubble

A

bidirectional

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13
Q

prokaryotes have a ______ origin of replication

A

single, because they have a circular genome!

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14
Q

eukaryotes have _______ origins of replication

A

multiple, because they have linear DNA

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15
Q

in what order do these proteins work in DNA replication?
- DNA polymerase III
-DNA polymerase I
- helicase
- primase
- SSB
- DNA topoisomerase
- DNA ligase

A
  1. DNA topoisomerase
  2. Helicase
  3. SSB
  4. Primase
  5. DNA poly III
  6. DNA poly I
  7. DNA ligase
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16
Q

what does DNA topoisomerase do?

A

relaxes supercoiling

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17
Q

what does helicase do?

A

unwinds the double helix

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18
Q

what does SSB do?

A

prevents re-annealing of separated strands

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19
Q

what does primase do?

A

synthesizes RNA primers

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20
Q

what does DNA poly III do?

A

synthesizes DNA

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21
Q

what does DNA poly I do?

A

removes and replaces RNA primer with DNA (cuts out nucleotides)

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22
Q

what does DNA ligase do?

A

joins DNA segments together

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23
Q

what direction is the template strand read in DNA replication?

A

3’ - 5’, new strand elongates in the 5’ -3’ direction!

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24
Q

most of the proteins/enzymes required for replication are apart of the complex called ______

A

replisome

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25
Q

replication is done in chunks… what are these “chunks” called?

A

okazaki fragments!

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26
Q

DNA polymerase I uses a 5’->3’ ______ activity to remove RNA nucleotides

A

exonuclease

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27
Q

DNA polymerase uses a 5’->3’ ______ activity to add DNA nucleotides

A

polymerase

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28
Q

true/false: DNA poly I and DNA ligase are active on both the leading and lagging strand

A

true! they’re just more prominent on the lagging strand

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29
Q

true/false: telomeres in prokaryotes

A

false! they’re only in eukaryotes

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30
Q

germ-line cells contain ____ that adds repetitive DNA sequences to the ends of telomeres

A

telomerases (enzyme containing RNA)

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31
Q

what is the Hayflick limit?

A

the number of repetition cycles in a cell’s life span (~50-70 cycles)

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32
Q

each successful replication ______ the telomeres in somatic cells

A

shortens

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33
Q

what is the central dogma of genetics?

A

the flow of heredity information (DNA -> transcription -> RNA -> translation -> protein)

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34
Q

______: DNA is converted to mRNA

A

transcription

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35
Q

in transcription, the new RNA molecule is synthesized via _________

A

RNA polymerase

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36
Q

what are the three stages of transcription?

A
  1. initiation
  2. elongation
  3. termination
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37
Q

what is the complementary DNA strand to the template strand called?

A

coding strand

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38
Q

______ are regions on the DNA template strand that RNA polymerase recognizes and initiates transcription

A

promoters

39
Q

transcription ends at _____

A

termination sequences

40
Q

_____ are regions that are transcribed but will be removed before mRNA is translated (because they don’t code for specific proteins)

A

introns

41
Q

_____ are regions that are transcribed and code for proteins, so remain in the translated mRNA

A

exons

42
Q

_______ has 5 subunits: 2 alpha subunits, 2 beta subunits and 1 omega subunit

A

RNA polymerase core

43
Q

how does RNA polymerase switch to its active form? (forming the closed promoter complex)

A

by binding to a sixth subunit (polypeptide) called “sigma subunit”

44
Q

what are the two promoter region codes for bacteria?

A
  1. 5’-TATAAT-3’
  2. 5’-TTGACA-3’
45
Q

when DNA unwinds near the transcription site it forms the ______

A

open promoter complex

46
Q

true/false: transcription isn’t as fast as translation

A

true

47
Q

true/false: instead of remaining unwound, during transcription the DNA immediately returns to a helix after RNA polymerase passes by

A

true

48
Q

what are the two termination mechanisms in bacterial transcription?

A
  1. intrinsic terminators
  2. rho-dependant
49
Q

how many RNA polymerases do eukaryotes have?

A

three

50
Q

RNA poly I transcribes: _____
RNA poly II transcribes: _____
RNA poly III transcribes: _____

A
  1. rRNA
  2. mRNA
  3. tRNA
51
Q

what are the promoter region sequences that RNA poly II bind to in eukaryotes?

A

TATA box (25 bases upstream of start site)
CAAT box (80 bases upstream)
GC-rich box (90 bases upstream)

52
Q

________ help bind the RNA polymerase to the DNA promoter regions

A

transcription factors

53
Q

__________ are DNA regulatory sequences that increase gene transcription (give promoter a “boost”!)

A

enhancer sequences

54
Q

____ repress transcription

A

silencer sequences

55
Q

_____ state also affects/regulates transcription

A

chromosome

56
Q

what kind of chromatin is actively transcribed? which kind cannot be transcribed?

A
  1. Euchromatin
  2. Heterochromatin
57
Q

when does termination occur in eukaryotes?

A

once RNA polymerase transcribes the poly-A tail, there’s no specific “stop” sequences like in bacteria

58
Q

how is pre-mRNA modified before being exported from the nucleus?

A

addition of a 5’ cap
addition of poly-A tail
splicing (removes introns, joins exons together)

59
Q

how long is a poly-A tail?

A

20-200 base pairs

60
Q

______: takes the message from mRNA and makes proteins

A

translation

61
Q

where does translation occur? (where are polypeptides assembled)

A

ribosomes

62
Q

what is the start codon for translation?

A

5’-AUG-3’

63
Q

which way does translation occur?

A

5’-3’

64
Q

which two regions of mRNA are not translated?

A
  1. 5’-untranslated region
  2. 3’-untranslated region
65
Q

what are the four main classifications of protein structure?

A

primary, secondary, tertiary, quaternary structure

66
Q
  1. peptidyl site (P site)
  2. aminoacyl site (A site)
  3. exit site (E site)

are all components of the _________ that contribute to _______

A
  1. large and small ribosomal subunits
  2. translation
67
Q

what does the P site in the ribosome do?

A

holds the tRNA containing the growing polypeptide

68
Q

what does the A site in the ribosome do?

A

binds the new tRNA molecule

69
Q

what does the E site in the ribosome do?

A

where tRNA’s leave the ribosome

70
Q

what are the three stop codons in eukaryotic translation?

A

UAG, UGA, UAA

71
Q

true/false: translation can happen simultaneously and continuously

A

true! it’s fast and very efficient

72
Q

each bacterial cell contains ~20 000 ribosomes which is about ____ of the cell’s mass

A

1/4

73
Q

true/false: the genetic code is redundant

A

true, many different codes for the same amino acid (doesn’t really matter which one)

74
Q

why is there a 3rd base wobble in tRNA anticodons?

A

so that it gives flexibility in case of mutation, if only the last position is altered, we can still code for the proper amino acid

75
Q

complementary base-pairing between the mRNA and tRNA is _______ and __________

A

anti-parallel and complimentary

76
Q

______: mutations are passed from one generation to the next

A

germ-line mutations

77
Q

____: mutations can alter subsequent generations of cells due to mitosis but AREN’T passed down to further generations

A

somatic mutation

78
Q

_______: mutation confined to a specific base-pair or gene location

A

point mutations

79
Q

what are the different “levels” of a point mutation?

A

amino acid level
RNA level
DNA level

80
Q

what do we call point mutations at the amino acid level?

A

synonymous, non-synonymous

81
Q

what do we call point mutations at the RNA level?

A

missense (nonsyn), silent (syn), nonsense (nonsyn), stop

82
Q

what do we call point mutations at the DNA level?

A

substitutions (transition/transversion) (syn), insertions/deletions (frameshifts) (nonsyn)

83
Q

purine -> purine
pyrimidine ->pyrimidine
this is what kind of mutation at the DNA level?

A

transition

84
Q

purine ->pyrimidine
is what kind of mutation at the DNA level?

A

transversion

85
Q

silent mutations are considered _______ because they do not affect the function of the protein

A

neutral mutations

86
Q

______: results in a premature stop

A

nonsense mutation, protein function is vastly different

87
Q

______: base-pair substitution that results in an amino acid change (usually a result of transversion)

A

missense mutation

88
Q

_____/______: result in the altering of the reading frame

A

insertions/deletions

89
Q
  1. promoter mutations
  2. splicing mutations
  3. cryptic splice sites
    are all examples of ________ mutations
A

regulatory mutations

90
Q

where do regulatory mutations occur?

A

in the non-coding region of genes (untranslated regions of mRNA)

91
Q

_____: alter consensus sequence nucleotides and interferes with efficient transcription initiation (not making as much mRNA -> alters level of gene expression)

A

promoter mutations

92
Q

_____: disrupt existing splice sites, create new ones, or activate the cryptic ones

A

splicing mutations

93
Q

______: certain base-pair substitutions create new splice sites that replace or compete with the authentic splice sites in pre-mRNA processing (accidentally introduce early splice site)

A

cryptic splice sites

94
Q

why are mutations important?

A
  1. increases genetic variation
  2. point mutations affect phenotypes by changing amino acid sequence

Genetics 1 (11 decks)

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