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IMAT Bio > Chapter 6: Nucleic Acid. The Central Dogma > Flashcards

Chapter 6: Nucleic Acid. The Central Dogma Flashcards

1
Q

What is the central dogma of molecular biology?

A

DNA → RNA → Protein

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2
Q

How do nucleosomes help DNA?

A

They help supercoil DNA.

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3
Q

What suggested the mechanism for DNA replication?

A

DNA structure.

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4
Q

In which direction can DNA polymerases add nucleotides?

A

3’ end of a primer.

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5
Q

How does DNA replication differ between the leading and lagging strands?

A

Continuous on leading; discontinuous on lagging.

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6
Q

What is the role of regions of DNA that do not code for proteins?

A

They have other important functions (regulation, structural, etc.)

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7
Q

What experiment concluded that DNA is the genetic material in bacteriophages?

A

Hershey and Chase experiment.

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8
Q

What are the three components of a nucleotide?

A

Nitrogen base, pentose sugar, phosphate group.

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9
Q

What are the four nitrogen bases in DNA?

A

Adenine, thymine, guanine, cytosine.

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10
Q

What are the four nitrogen bases in RNA?

A

Adenine, uracil, guanine, cytosine.

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11
Q

What is the structure of RNA?

A

Single strand of nucleotides.

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12
Q

What type of bonds connect DNA strands?

A

Hydrogen bonds.

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13
Q

Which nitrogen bases are complementary in DNA?

A

A-T (2 H-bonds), G-C (3 H-bonds).

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14
Q

What direction do the two strands of DNA run?

A

Antiparallel (5’→3’ and 3’→5’).

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15
Q

What links the sugar molecules in a strand of DNA?

A

Phosphodiester bonds.

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16
Q

What are purines and pyrimidines in DNA?

A

Purines: A, G; Pyrimidines: T, C.

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17
Q

What is a gene?

A

A DNA sequence coding for one polypeptide.

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18
Q

What causes genetic mutations?

A

Changes in a gene’s nucleotide sequence.

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19
Q

What are alleles?

A

Variants of a gene caused by mutations.

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20
Q

Where does DNA replication occur?

A

In the nucleus.

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21
Q

What enzymes are required for DNA replication?

A

Helicase, DNA polymerase.

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22
Q

What does helicase do during DNA replication?

A

Breaks hydrogen bonds.

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23
Q

What is the role of DNA polymerase in replication?

A

Forms phosphodiester bonds in the new strand.

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24
Q

What is the semi-conservative model of DNA replication?

A

Each new DNA has one original strand.

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25
Q

How does bacterial DNA differ from eukaryotic DNA in replication?

A

Bacterial: circular, one origin, no histone; Eukaryotic: linear, multiple origins, histone.

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26
Q

What is the function of DNA gyrase?

A

Stabilizes DNA helix during unzipping.

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27
Q

What produces a primer during DNA replication?

A

Primase.

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28
Q

What replaces RNA primers with DNA nucleotides?

A

DNA polymerase I.

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29
Q

What joins Okazaki fragments?

A

DNA ligase.

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30
Q

In what direction is DNA synthesized?

A

5’ to 3’ direction.

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31
Q

How is the DNA code carried to ribosomes?

A

By mRNA.

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32
Q

Where does transcription occur?

A

In the nucleus.

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33
Q

What strand of DNA is used during transcription?

A

Anti-sense strand.

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34
Q

What enzyme is key in transcription?

A

RNA polymerase.

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35
Q

Where does transcription begin and end on DNA?

A

Begins at promoter, ends at terminator.

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36
Q

How does mRNA compare to the DNA it is transcribed from?

A

Single-stranded, shorter, complementary to one gene.

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37
Q

Where does translation occur?

A

Cytosol or rough ER.

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38
Q

What is the role of tRNA in translation?

A

Brings specific amino acids to ribosomes.

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39
Q

What does the genetic code determine?

A

Sequence of amino acids in polypeptides.

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40
Q

What is the start codon and its amino acid?

A

AUG; Methionine.

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41
Q

What are stop codons?

A

UAA, UAG, UGA.

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42
Q

What does ‘genetic code is degenerate’ mean?

A

Multiple codons can code for the same amino acid.

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43
Q

What does ‘genetic code is universal’ mean?

A

Same code in nearly all organisms.

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44
Q

What are ribosomes made of?

A

rRNA and proteins.

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45
Q

How many bases does a ribosome expose at a time during translation?

A

Six bases.

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46
Q

What enzyme catalyzes peptide bond formation during translation?

A

Peptidyl transferase.

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47
Q

What happens when a stop codon is reached during translation?

A

The polypeptide chain is released.

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48
Q

Why do cells differ if they all have the same DNA?

A

Different gene expression.

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49
Q

What is gene expression?

A

Turning on a gene to produce RNA and protein.

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50
Q

At what levels can gene expression be regulated?

A

Epigenetic, transcriptional, post-transcriptional, translational, post-translational.

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51
Q

How is prokaryotic gene expression regulated?

A

At the transcriptional level.

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52
Q

How is eukaryotic gene expression regulated?

A

During transcription, RNA processing, translation, and post-translation.

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53
Q

What is the relationship between histones and DNA?

A

DNA (negative) binds to positively charged histones.

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54
Q

What is the effect of DNA methylation?

A

Deactivates gene expression.

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55
Q

What type of DNA is highly methylated?

A

Inactive DNA.

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56
Q

What are introns and exons?

A

Introns: non-coding regions; Exons: coding regions.

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57
Q

What happens to introns during splicing?

A

They are removed.

58
Q

What is added to mRNA during splicing?

A

Cap and poly-A tail.

59
Q

What allows a single gene to produce multiple proteins?

A

Alternative splicing.

60
Q

What do transcription factors do?

A

Bind DNA and regulate RNA polymerase binding.

61
Q

What are structural genes?

A

Genes coding for proteins.

62
Q

What are regulatory genes?

A

Genes controlling expression of other genes.

63
Q

What is an operon?

A

Unit of gene expression in bacteria.

64
Q

What are the structural genes in the lac operon?

A

lacZ, lacY, lacA.

65
Q

What does lacZ code for?

A

β-galactosidase.

66
Q

What does lacY code for?

A

Permease.

67
Q

What does lacA code for?

A

Transacetylase.

68
Q

What is the function of a regulatory gene in the lac operon?

A

Codes for the repressor protein.

69
Q

What happens to the lac operon when lactose is absent?

A

Repressor binds to the operator; no transcription occurs.

70
Q

What happens to the lac operon when lactose is present?

A

Lactose binds the repressor, allowing transcription.

71
Q

What is the shape of bacterial DNA?

A

Circular.

72
Q

How many origins of replication are in bacterial DNA?

A

One.

73
Q

What is the shape of eukaryotic DNA?

A

Linear.

74
Q

How many origins of replication are in eukaryotic DNA?

A

Thousands.

75
Q

What enzyme unzips DNA during replication?

A

Helicase.

76
Q

What bonds are broken by helicase during DNA replication?

A

Hydrogen bonds.

77
Q

What do free nucleotides do during DNA replication?

A

Pair with template strands.

78
Q

What is the direction of DNA strand elongation?

A

5’ to 3’.

79
Q

What removes primers during DNA replication?

A

DNA polymerase I.

80
Q

What connects Okazaki fragments?

A

DNA ligase.

81
Q

What are Okazaki fragments?

A

Short DNA segments on the lagging strand.

82
Q

What enzyme stabilizes the DNA helix during unzipping?

A

DNA gyrase.

83
Q

What is the function of RNA primase in DNA replication?

A

Produces RNA primers.

84
Q

What is the template strand in transcription called?

A

Anti-sense strand.

85
Q

Where does the RNA polymerase bind to initiate transcription?

A

Promoter.

86
Q

What terminates transcription?

A

Terminator sequence.

87
Q

What is the first codon in mRNA translation?

A

AUG.

88
Q

What amino acid does AUG code for?

A

Methionine.

89
Q

How many codons code for stop signals?

A

Three.

90
Q

What is the role of tRNA’s anticodon?

A

Binds to complementary mRNA codon.

91
Q

How many codons are in the genetic code?

A

64 codons.

92
Q

What makes the genetic code universal?

A

Same code in most organisms.

93
Q

What does epigenetic regulation involve?

A

Modifying DNA or histones.

94
Q

What does post-transcriptional regulation include?

A

Splicing, RNA modification.

95
Q

What happens in post-translational regulation?

A

Protein modifications.

96
Q

What is the role of permease in the lac operon?

A

Allows lactose to enter the cell.

97
Q

What is the function of β-galactosidase in the lac operon?

A

Hydrolyzes lactose into glucose and galactose.

98
Q

What type of binding sites does the lac operon repressor protein have?

A

DNA-binding and lactose-binding sites.

99
Q

What happens when lactose binds to the lac operon repressor?

A

Repressor shape changes, preventing it from binding DNA.

100
Q

What is the role of RNA polymerase in the lac operon?

A

Transcribes structural genes when repressor is inactive.

101
Q

What is epigenetic modification?

A

Changes to DNA/histones affecting gene expression.

102
Q

What effect does histone modification have on DNA?

A

Alters how tightly DNA is wound.

103
Q

What group is added during DNA methylation?

A

Methyl group (-CH3).

104
Q

What does heavily methylated DNA indicate?

A

Inactive gene expression.

105
Q

What does pre-mRNA contain in eukaryotes?

A

Introns and exons.

106
Q

What happens during splicing?

A

Introns are removed, and exons may be rearranged.

107
Q

What is added to pre-mRNA to form mature mRNA?

A

A cap and a poly-A tail.

108
Q

What is the lac operon an example of?

A

Gene regulation in prokaryotes.

109
Q

How are transcription and translation coupled in prokaryotes?

A

They occur simultaneously in the cytoplasm.

110
Q

Where does eukaryotic transcription occur?

A

In the nucleus.

111
Q

Where does eukaryotic translation occur?

A

In the cytoplasm.

112
Q

What ensures proper protein folding after synthesis?

A

Post-translational modifications.

113
Q

What is the main difference between bacterial and eukaryotic transcription?

A

Eukaryotes have RNA processing; bacteria do not.

114
Q

What do structural genes code for?

A

Proteins.

115
Q

What is the role of regulatory genes?

A

Control expression of other genes.

116
Q

What is the significance of the operator in the lac operon?

A

Binding site for the repressor protein.

117
Q

What is the function of transacetylase in the lac operon?

A

Function is less clear; may detoxify compounds.

118
Q

What is a ‘degenerate’ genetic code?

A

Multiple codons code for the same amino acid.

119
Q

Why is the genetic code considered nearly universal?

A

It is shared by most organisms.

120
Q

What is the promoter’s role in transcription?

A

It is where RNA polymerase binds to start transcription.

121
Q

What regulates RNA polymerase activity in prokaryotes?

A

Repressor proteins and operator regions.

122
Q

What happens when a stop codon is exposed during translation?

A

Translation ends, and the polypeptide is released.

123
Q

What components are needed for translation?

A

mRNA, tRNA, ribosome, and amino acids.

124
Q

How does alternative splicing increase protein diversity?

A

By rearranging exons to create different mRNA variants.

125
Q

What is a codon?

A

A sequence of three nucleotides in mRNA.

126
Q

What binds to a codon during translation?

A

tRNA anticodon.

127
Q

What is the first step of translation?

A

mRNA binds to the ribosome.

128
Q

What happens in the elongation step of translation?

A

Peptide bonds form between amino acids.

129
Q

What happens in the termination step of translation?

A

A stop codon signals the end of translation.

130
Q

What ensures DNA replication accuracy?

A

Repair enzymes detect and fix errors.

131
Q

What allows bacterial cells to regulate gene expression efficiently?

A

Operons like the lac operon.

132
Q

What are histones?

A

Proteins that DNA wraps around.

133
Q

What is chromatin?

A

DNA-protein complex in the nucleus.

134
Q

How does RNA differ from DNA structurally?

A

RNA has ribose and uracil; DNA has deoxyribose and thymine.

135
Q

What is the role of mRNA?

A

Carries genetic code from DNA to ribosomes.

136
Q

What is the role of rRNA?

A

Forms part of the ribosome’s structure.

137
Q

What is the role of tRNA?

A

Brings amino acids to the ribosome.

138
Q

What is the universal start codon?

A

AUG.

139
Q

How are transcription and translation related?

A

Transcription creates mRNA; translation uses mRNA to make proteins.

140
Q

What is the primary function of DNA?

A

Store genetic information.

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