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Biochemistry-First Aid 2017 > Molecular > Flashcards

Molecular Flashcards

1
Q

How many times does DNA loop around histone octamer to form nucleosome?

A

Twice

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2
Q

Histones are rich in what two amino acids?

A

Lysine and arginine

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3
Q

Which histone is responsible for stabilizing the chromatin fiber

A

H1

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4
Q

DNA and histone synthesis occur in what cell cycle phase?

A

S-phase

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5
Q

Barr bodies have what type of chromatin structure?

A

Heterochromatin

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6
Q

Which chromatin is transcriptionally active?

A

Euchromatin

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7
Q

What inactivates transcription and increases condensation of chromatin?

A

Increased methylation and decreased acetylation

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8
Q

What is methylated on DNA to suppress transcription

A

CpG islands

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9
Q

What is the purpose of cytosine and adenine methylation during DNA replication

A

Allows DNA repair enzymes in prokaryotes to distinguish old from new strand in DNA replication

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10
Q

What relaxes DNA coiling allowing transcription

A

Histone acetylation

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11
Q

What usually reversibly represses DNA transcription

A

Histone methylation

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12
Q

Phosphodiester bonds in nucleotides are linked in what direction

A

3’ to 5’ direction

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13
Q

What end of the nucleotide has the triphosphate group?

A

5’ end

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14
Q

What is the target of the nucleotide 3’ hydroxyl group?

A

Nucleotide triphosphate bond

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15
Q

Purines are composed of how many rings

A

One

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16
Q

What are the purines

A

Adenine and Guanine

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17
Q

Which nucleotide has a methyl group?

A

Thymine

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18
Q

Deamination of what nucleotide makes uracil

A

Cytosine

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19
Q

Deamination of what nucleotide makes guanine

A

Adenine

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20
Q

Methylation of what makes thymine?

A

Uracil

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21
Q

What increases the melting temperature of DNA

A

Increased G-C bonding

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22
Q

How many bonds are formed between C-G

A

3 bonds

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23
Q

Amino acids necessary for purine synthesis

A

Glycine, Aspartate, Glutamine (GAG)

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24
Q

Ribose-5-phosphate for purine synthesis is derived from what pathway

A

PPP

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25
Q

The first step of the pyrimidine/purine pathway involves what?

A

Ribose-5-P converted to PRPP by PRPP synthetase

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26
Q

PRPP can go into which two pathways?

A

Pyrimidine or purine pathway

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27
Q

In the purine pathway, what inhibits PRPP conversion to IMP?

A

6-mercaptopurine (6-MP) and its prodrug azathioprine

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28
Q

IMP in the purine pathway gets converted to what?

A

AMP or GMP

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29
Q

What enzyme converts AMP and GMP into uric acid

A

Xanthine oxidase

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30
Q

What drug inhibits dihydroorotate dehydrogenase

A

Leflunomide

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31
Q

What drug inhibits ribonucleotide synthetase

A

Hydroxyurea

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32
Q

What drug inhibits thymidylate synthase

A

5-fluorouracil

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33
Q

5-fluorouracil forms what intermediate to inhibit thymidylate synthase

A

5-F-dUMP

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34
Q

Inhibition of thymidylate synthase will cause a decrease in what product?

A

dTMP

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35
Q

Carbamoyl phosphate is made from glutamine and CO2 using what enzyme

A

Carbamoyl phosphate synthetase II

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36
Q

Orotic acid synthesis is inhibited by what drug

A

Leflunomide

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37
Q

What is impaired in orotic aciduria

A

Conversion of orotic acid to UMP

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38
Q

What inhibits the conversion of IMP to GMP

A

Mycophenolate or ribavirin

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39
Q

What enzyme is inhibited by mycophenolate

A

IMP dehydrogenase

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40
Q

Mycophenolate will cause a decrease in what product

A

GMP

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41
Q

Inhibition of dihydrofolate reductase by methotrexate prevents what

A

Conversion of DHF to THF

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42
Q

What drugs inhibit dihydrofolate reductase

A

Methotrexate, trimethoprim, and pyrimethamine

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43
Q

What is the function of ribonucleotide reductase

A

Convert ribose sugars into deoxyribose sugars for DNA synthesis

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44
Q

In rapidly diving cancer cells what drug is used to prevent the conversion of thymine, preventing DNA synthesis

A

5-Fluorouracil (5-FU)

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45
Q

In a bacterial infection, what drug is used to prevent the conversion of DHF to THF

A

Trimethoprim

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46
Q

What enzyme is required for the degradation of adenosine and deoxyadenosine?

A

Adenosine deaminase

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47
Q

What is a complication of adenosine deaminase deficiency

A

Increased dATP leading to toxicity in lymphocytes

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48
Q

What disease is associated with adenosine deaminase deficiency

A

SCID

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49
Q

What is the genetic inheritance of SCID

A

Autosomal recessive

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50
Q

Lesch-Nyhan syndrome is a defect in what pathway

A

Purine salvage pathway

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51
Q

What is the defect in Lesch-Nyhan syndrome

A

Absent HGPRT

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52
Q

What is the function of HGPRT in the purine salvage pathway

A

Convert hypoxanthine to IMP and guanine to GMP

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53
Q

What is the result of Lesch-Nyhan syndrome

A

Excess uric acid production and de novo purine synthesis

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54
Q

Intellectual disability, gout, dystonia, self-mutilation with aggression and hyperuricemia describe what syndrome

A

Lesch-Nyhan syndrome

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55
Q

What is the first-line treatment for Lesch-Nyhan syndrome

A

Allopurinol

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56
Q

What is the second-line treatment for Lesch-Nyhan syndrome

A

Febuxostat

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57
Q

What medication will inhibit uric acid excretion

A

Aspirin

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58
Q

What medication will increase uric acid excretion

A

Probenecid

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59
Q

What medication will prevent the synthesis of uric acid

A

Allopurinol

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60
Q

What medication will inhibit xanthine oxidase

A

Allopurinol or febuxostat

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61
Q

What nucleotides are used in the Purine salvage pathway

A

Guanine and Adenine

62
Q

DNA synthesis occurs in what direction

A

5’ to 3’ direction

63
Q

Unwinds DNA template at replication fork

A

Helicase

64
Q

What prevents strands from reannealing

A

Single-stranded binding proteins

65
Q

What create single or double stranded breaks in DNA helix to remove supercoils

A

DNA topoisomerases

66
Q

What makes an RNA primer on which DNA polymerase III can initiate replication

A

Primase

67
Q

DNA pol III proofreads in what direction

A

3’ to 5’ direction

68
Q

What is the function of primase

A

To make an RNA primer for DNA pol III

69
Q

DNA pol III synthesizes DNA in what direction

A

5’ to 3’ direction

70
Q

DNA pol I and pol III are used by what type of organisms

A

Prokaryotes only

71
Q

Catalyzes the formation of Phosphodiester bonds within a strand of dsDNA

A

DNA ligase

72
Q

Joins Okazaki fragments

A

DNA ligase

73
Q

RNA-dependent DNA polymerase that adds DNA to 3’ ends of chromosomes to avoid loss of chromosomal material with every duplication

A

Telomerase

74
Q

Eukaryotes have how many origins of replication

A

Multiple

75
Q

Elongates lagging strand until it reaches primer of preceeding fragment

A

DNA pol III

76
Q

Which type of Nucleotide substitution causes the most severe damage

A

Frameshift mutation

77
Q

What is a transversion mutation

A

Purine switched for pyrimidine or vice-versa

78
Q

Cause of most silent mutations

A

tRNA wobble in 3rd position of codon

79
Q

Nucleotide substitution that codes for the same amino acid

A

Silent mutation

80
Q

Sickle cell disease is what type of nucleotide substitution

A

Missense mutation

81
Q

What is a conservative missense mutation

A

Nucleotide substitution that codes for similar amino acid

82
Q

Nucleotide substitution that codes for different amino acid

A

Missense mutation

83
Q

What amino acids are substituted in sickle cell disease

A

Glutamine to Valine at position 6

84
Q

Nucleotide substitution resulting in a stop codon

A

Nonsense mutation

85
Q

Type of mutation that usually results in nonfunctional protein

A

Nonsense mutation

86
Q

UAG, UAA, UGA are what type of codons

A

Stop codons

87
Q

Nucleotide substitution resulting in misreading of all nucleotides downstream

A

Frameshift mutation

88
Q

Tay-Sachs disease and Duchenne muscular dystrophy are examples of what type of nucleotide substitution

A

Frameshift mutation

89
Q

Direction of protein synthesis

A

N-terminus to C-terminus

90
Q

Responsible for posttranscriptional regulation of gene expression by targeting 3’ untranslated region of specific mRNAs for degradation or translational repression

A

microRNAs

91
Q

Function of alternate splicing

A

Combine different axons to make unique proteins

92
Q

Intervening noncoding segments of transcript

A

Introns

93
Q

Part of transcript that contains actual genetic information coding for proteins

A

Exon

94
Q

Antibodies to spliceosomal snRNPs (anti-Smith antibodies) are highly specific for what disease

A

SLE

95
Q

Primary transcript combines with snRNPs and other proteins to form what

A

Spliceosome

96
Q

AAUAAA does what to RNA

A

Adds poly-A tail to RNA molecule

97
Q

Site of RNA 5’ capping, addition of poly-A 3’ tail, and splicing of RNA molecule

A

Nucleus

98
Q

Where does translation of mRNA occur

A

Cytosol

99
Q

RNA pol that makes tRNA

A

RNA pol III

100
Q

Types of polymerase in prokaryotes

A

1 type for all RNA molecules

101
Q

Types of polymerase in eukaryotes

A

RNA pol I-III

102
Q

RNA pol that makes mRNA

A

RNA pol II

103
Q

Smallest RNA molecule

A

tRNA

104
Q

RNA pol that makes rRNA

A

RNA pol I

105
Q

Largest RNA molecule

A

mRNA

106
Q

alpha-amanitin found in death cap mushroom inhibits what RNA pol

A

RNA polymerase II resulting in decreased mRNA

107
Q

Site of repressor binding

A

Silencer

108
Q

Where do activator proteins bind to

A

Enhancer region for alteration of transcription

109
Q

Site of DNA that alters gene transcription by binding transcription factors

A

Enhancer

110
Q

What is contained in the Promoter region

A

CAAT and TATA boxes

111
Q

Site where RNA pol II and other transcription factors bind to DNA upstream from gene locus

A

Promoter

112
Q

What does a promoter mutation result in?

A

Decrease in level of gene transcription

113
Q

Codes for methionine which may be removed before translation is complete in eukaryotes

A

AUG

114
Q

mRNA start codon

A

AUG

115
Q

DNA repair mechanism defective in ataxia telangiectasia

A

Non-homologous end joining

116
Q

What DNA repair mechanism is defective in Lynch syndrome

A

Mismatch repair

117
Q

Nucleotide excision repair occurs in what cell cycle phase

A

G1 phase

118
Q

What is responsible for repair of pyrimidine dimers formed from excessive UV light

A

Nucleotide excision repair

119
Q

What conditions cause basal expression of Lac gene

A

High glucose, lactose available

120
Q

What conditions cause Lac gene to not be expressed

A

High glucose, lactose unavailable and low glucose, lactose unavailable

121
Q

What conditions cause Lac gene to be expressed

A

Low glucose, lactose available

122
Q

Splice site mutations may result in what type of diseases

A

Some cancers and beta-thalassemias, dementia and epilepsy

123
Q

Protein with impaired or altered function is typically a result of what type of DNA mutation

A

Splice site mutation

124
Q

Type of mutation resulting in retained intron in mRNA

A

Splice site mutation

125
Q

Promoter region is located upstream from what?

A

Gene locus

126
Q

What is responsible for scrutinizing amino acid before and after it binds to tRNA

A

Aminoacyl-tRNA synthetase

127
Q

Aminoacyl-tRNA binds to what on tRNA molecule

A

A site

128
Q

What catalyzes peptide bond formation in a growing polypeptide

A

rRNA

129
Q

What part of the ribosome accommodates growing peptide

A

P site

130
Q

Ribosome advances 3 nucleotides toward what end of the mRNA

A

3’ end

131
Q

What holds empty tRNA as it exits ribosome

A

E site

132
Q

What transfers growing peptide to amino acid in A site

A

Ribozyme (rRNA)

133
Q

Intracellular protein involved in facilitating and/or maintaining protein folding

A

Chaperon proteins

134
Q

HSP60 is what type of protein

A

Chaperone protein

135
Q

Process that removes N-terminus or C-terminus from zymogen to generate mature protein

A

Trimming

136
Q

Covalent alterations are what type of modifications

A

Posttranslational modifications

137
Q

What part of tRNA accepts the amino acid

A

CCA end located on 3’ end

138
Q

Section of tRNA located opposite 3’ aminoacyl end

A

Anticodon

139
Q

Binds tRNA molecule to the ribosome

A

T arm of tRNA molecule

140
Q

Contains dihydrouridine residues necessary for tRNA recognition by the correct aminoacyl-tRNA synthetase

A

D arm of tRNA molecule

141
Q

Activation of tRNA molecule converts ATP into what

A

AMP + Pi

142
Q

What is required for the initiation phase of protein synthesis

A

Initiation factors and GTP

143
Q

What happens during the initiation phase of protein synthesis

A

40s ribosomal subunit is attached with the initiator tRNA and released when to mRNA and the 60s subunit assemble with the complex

144
Q

Moving peptidyl tRNA from A site to P site

A

Translocation

145
Q

Macrolides mechanism of action

A

Target prokaryotic 50s ribosomal subunit - prevent Elongation

146
Q

Aminoglycosides mechanism of action

A

Target prokaryotic 30s ribosomal subunit - prevent Initiation

147
Q

Chloramphenicol mechanism of action

A

Block prokaryotic 50s ribosomal subunit

148
Q

Tetracyclines mechanism of action

A

Block prokaryotic 30s ribosomal subunit

149
Q

Clindamycin mechanism of action

A

Block prokaryotic 50s ribosomal subunit

150
Q

DNA has what type of charge

A

Negative

151
Q

Histones have what type of charge

A

Positive

Biochemistry-First Aid 2017 (5 decks)

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