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Immunology & Virology > Basic Concepts > Flashcards

Basic Concepts Flashcards

1
Q

Replication

A

both strands are templates for new DNA synthesis

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2
Q

Transcription

A

dark green strand is template for RNA synthesis

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3
Q

Translation

A

messenger RNA is template for protein synthesis

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4
Q

Genetic information in the cell is held by information molecules EXCEPT

A

phospholipids

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5
Q

The functional unit of genetic information is the

A

gene

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6
Q

DNA-binding proteins interact predominantly within which portion of a double-stranded DNA helix?

A

major groove

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7
Q

AT-rich DNA will denature/melt

A

at a lower temperature than GC-rich DNA

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8
Q

Supercoiling is important for DNA structure, because

A

it condenses the DNA so that it can fit inside the cell

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9
Q

In all cells, genes are composed of

A

nucleic acids.

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10
Q

GTP provides energy for

A

translation

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11
Q

The flow of biological information begins with

A

DNA replication

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12
Q

DNA participates in protein synthesis through

A

an RNA intermediate

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13
Q

The two strands of the DNA double helix are held together by

A

hydrogen bonds between nucleotide bases

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14
Q

You experimentally change the DNA sequence directly upstream of a start codon of an operon in E. coli to investigate the function of this region of DNA. Analysis reveals that after the change the same amount of mRNA is made from the operon, but there are very few proteins made from the operon. What is the most likely function of the DNA sequence that you changed?

A

The DNA sequence likely functions as a ribosome-binding site.

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15
Q

In ________ several ribosomes can simultaneously translate a single mRNA molecule in a complex called a(n) ________.

A

prokaryotes / polysome

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16
Q

Each adenine-thymine base pair has ________ hydrogen bonds, while each guanine-cytosine base pair has ________ hydrogen bond(s).

A

two / three

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17
Q

List the steps of the central dogma of molecular biology in the correct order.

A

DNA → RNA → protein

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18
Q

RNA acts at both the genetic and the functional levels.

A

True

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19
Q

rRNA has an enzymatic role in all stages of protein synthesis.

A

True

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20
Q

A plasmid differs from the bacterial chromosome in that it is __________.

A

significantly smaller

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21
Q

Plasmids function in bacterial cells to __________.

A

confer to a cell additional genetic traits that are needed only under certain circumstances

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22
Q

How are plasmids different than chromosomes?

A

Plasmids contain genes that are NOT essential for cellular growth and replication.

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23
Q

Genes that are encoded for polymerases, gyrases, ribosomal proteins, and other proteins essential to replication, transcription, and translation are present on

A

chromosomes

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24
Q

In Bacteria, a chromosome can be distinguished from a plasmid, because a chromosome is a genetic element that

A

encodes for essential functional genes

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25
Q

Which statement best describes an operon?

A

several genes, next to each other in prokaryotic DNA, that are transcribed as a single piece of mRNA

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26
Q

Match the bacterial genetic element with the correct characteristic.

A

plasmid – nonessential genes

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27
Q

Most prokaryotic genomes are double-stranded circular DNA.

A

True

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28
Q

Explain the concept of semiconservative replication and how simultaneous copying of both strands of DNA is accomplished in prokaryotic cells.

A

One parent strand that is conserved and a daughter strand that is newly created can be combined into one strand through the unzipping and complementary strand formation processes of DNA replication. DNA can be conserved while being copied thanks to the replication bubble and two-way replication.

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29
Q

DNA replication always proceeds in only one direction because the ________ of the incoming nucleotide is attached to the free ________ of the growing DNA strand.

A

5-phosphate / 3-hydroxyl

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30
Q

Which of the following is formed on the lagging strand during DNA synthesis?

A

Okazaki fragments

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31
Q

Which of the following is NOT correct regarding DNA and RNA synthesis?

A

Both processes require an RNA primer to begin.

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32
Q

The function of the DNA polymerase is to catalyze

A

the addition of deoxynucleotides.

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33
Q

DNA replication is started with a(n) ________, which, in most cases, in vivo is a short stretch of ________.

A

primer / RNA

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34
Q

During DNA replication Okazaki fragments are linked together by ________, an enzyme that creates phosphodiester bonds between nicked fragments of DNA.

A

DNA ligase

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35
Q

In DNA replication there are leading and lagging strands, because

A

DNA replication is semiconservative and each strand is copied simultaneously in opposite directions.

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36
Q

Which statement illustrates why DNA polymerase cannot initiate a new DNA strand?

A

DNA polymerase requires a preexisting 3’-hydroxyl group in order to add nucleotides.

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37
Q

The formation of new DNA does NOT require energy.

A

False

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38
Q

DNA replication involves the synthesis of an RNA primer on one strand of the DNA.

A

True

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39
Q

Which enzyme breaks the hydrogen bonds during replication?

A

DNA helicase

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40
Q

How do stabilizing proteins work on the DNA?

A

They bind to the single-stranded DNA.

41
Q

In which direction does the replication fork move?

A

It moves ahead of the newly synthesized DNA.

42
Q

What ensures that the single strands of DNA do not come back together?

A

Stabilizing proteins

43
Q

What are the products of semiconservative replication for a double-stranded DNA molecule?

A

Two double-stranded DNA molecules, each consisting of one parental strand and one daughter strand.

44
Q

Why is DNA replication essential for a cell?

A

An organism must copy its DNA to pass genetic information to its offspring.

45
Q

What is the function of the parental DNA in replication?

A

It serves as the template for DNA replication.

46
Q

Why must primase be used before DNA polymerase when replicating DNA?

A

Primase provides an RNA primer with a 3’ end on which DNA polymerase can act.

47
Q

Which enzyme joins the gaps between synthesized DNA fragments of the lagging strand?

A

DNA ligase

48
Q

Which strand will require more RNA primers to complete synthesis?

A

Lagging strand

49
Q

In which direction does DNA polymerase synthesize DNA for the lagging strand?

A

5’ to 3’

50
Q

What characteristic of DNA allows two connected DNA polymerases to synthesize both the leading and lagging strands?

A

DNA is flexible

51
Q

What is the function of the connector proteins?

A

They link the leading strand DNA polymerase and the lagging strand DNA polymerase together.

52
Q

Which DNA strand is synthesized continuously?

A

Leading strand

53
Q

Which of the following are terms associated with Okazaki fragments?

A

Lagging strand, DNA ligase, and discontinuous

54
Q

Why is the DNA synthesis of the lagging strand considered discontinuous?

A

The synthesis is moving in the opposite direction from the replication fork.

55
Q

Proofreading of newly-synthesized DNA is important because __________.

A

a high fidelity in the copying of DNA is necessary for good heredity

56
Q

Events occurring in this bacterial transcription process.

A
  1. sigma factor recognizes promoter and initiation site
  2. transcription begins; sigma factor released’ RNA chain grows
  3. termination site reached’ chain growth stops
  4. polymerase and RNA are released
57
Q

In E. coli, the consensus sequence for the Pribnow box (the -10 sequence) is TATAAT. Therefore, __________.

A

this will be the strongest -10 promoter sequence

58
Q

The template for RNA polymerase is ________, and the new RNA molecule is ________ to the template.

A

DNA / antiparallel and complementary

59
Q

In the process of transcription, promoters are specific sequences of ________ that are recognized by ________.

A

DNA / sigma factors

60
Q

An example of correct nucleotide pairing is

A

A and T.

61
Q

Termination of RNA synthesis is ultimately determined by

A

specific nucleotide sequences on the template strand.

62
Q

The function of RNA polymerase is to

A

catalyze the formation of phosphodiester bonds between ribonucleotides.

63
Q

Polycistronic transcription units are common in

A

both Archaea and Bacteria.

64
Q

An operon is a useful genetic element, because it

A

allows coordinated expression of multiple related genes in prokaryotes.

65
Q

Which statement is the correct definition of polycistronic mRNA?

A

a single piece of mRNA that contains the transcript for multiple genes.

66
Q

Identify the events of RNA processing.

A
  1. a modified guanine nucleotide is added to the beginning of the RNA strand as a cap
  2. segments of the RNA strand that do not actually code for the protein are removed
  3. segments of the RNA that do not code for the protein are reconnected
  4. extra adenine nucleotides are added to the end of the RNA strand, forming a tail
  5. the completed mRNA leaves the nucleus
67
Q

Explain the difference between transcription and translation and how the processes differ in bacteria and eukaryotes.

A

In eukaryotic species, translation takes place in the cytoplasm and endoplasmic reticulum while transcription takes place in the nucleus. Prokaryotes carry out both activities in their cytoplasm. Both transcription and translation are regulated by RNA polymerase, which is also responsible for translation.

68
Q

Speculate on why it can be problematic to copy and express genes from Bacteria into Eukarya.

A

Contrary to prokaryotes, where gene expression is regulated at the transcriptional level, the eukaryotic genome’s method for gene expression is a complex process. In prokaryotes, the production of the fa protein is dependent on the needs of the cell; in other words, the genes are continually expressed when there is a need for it and stop when there isn’t. Contrarily, the transcription and translation processes are independently controlled by cellular barriers in eukaryotic cells, which is not the case in bacterial systems. The procedure is complicated by this decoupled approach and the regulation at every stage. In eukaryotic systems, the post-translational modification process is also distinct and may change the structure or folding conformation.

69
Q

Which of the following statements is TRUE concerning mRNA?

A

mRNA has a very short half-life.

70
Q

Many pharmaceutical drugs specifically inhibit transcription in Bacteria but not Archaea or Eukarya. Why would drugs that inhibit transcription only affect Bacteria and not Archaea even though they are both prokaryotes?

A

Archaea and Eukarya have very similar RNA polymerases that are different than bacterial RNA polymerases.

71
Q

Transcription in eukaryotes occurs in the

A

nucleus

72
Q

Polypeptides and proteins must fold properly to be functional. Hydrogen bonds between the oxygen and nitrogen atoms of the peptide bonds are crucial to which level of protein structure?

A

secondary structure

73
Q

Which statement illustrates how prokaryotes determine where to begin translation so the correct protein is synthesized?

A

The rRNA recognizes the correct start codon with the aid of an upstream Shine-Dalgarno sequence.

74
Q

The process of synthesizing proteins involves translating one “language,” nucleic acid sequences, into another “language,” amino acid sequences. The cellular component that does the actual translating from codons to amino acids is the __________.

A

tRNA

75
Q

Transfer RNA (tRNA) molecules

A

function to transfer the correct amino acids to the ribosome during translation.

76
Q

The codon on the ________ matches with the anticodon on the ________ to direct the addition of the correct amino acid to the growing polypeptide chain.

A

mRNA / tRNA

77
Q

Stop codons are also called ________ codons.

A

nonsense

78
Q

How is an open reading frame (ORF) identified and used to determine the sequence of amino acids in the gene it encodes for?

A

A sequence of nucleotides known as an ORF is defined as having a start codon (AUG on mRNA or ATG on DNA sense strand), a protein-encoding sequence, and a stop codon (UGA, UAA, UAG on mRNA or TGA, TAA, TGA on DNA sense strand).

The ribosomes recognize and bind to the mRNA transcript’s start codon during translation, move through the protein-encoding sequence, adding one amino acid to each synthesizing polypeptide that corresponds to the triplet codon, and stop translation when they reach the stop codon.

79
Q

tRNA is released from the ribosome at the ________ site.

A

E

80
Q

Which statement is TRUE regarding protein synthesis?

A

The 23S rRNA catalyzes peptide bond formation in the growing polypeptide chain.

81
Q

Which of the following is an example of one codon?

A

CAG

82
Q

In all cells a gene encodes for

A

a protein, tRNA, or rRNA depending on the specific gene.

83
Q

The structure and function of a protein are determined by its ________ sequence.

A

amino acid

84
Q

A triplet of bases on an mRNA molecule is known as a(n)

A

codon

85
Q

Throughout the living world, the genetic code is generally universal; however, there are slight variations.

A

True

86
Q

What results from the process of translation?

A

A polypeptide

87
Q

How is bacterial translation different from eukaryotic translation?

A

Bacteria can begin translation before transcription has terminated.

88
Q

According to the animation, ribosomes move along the mRNA in which direction?

A

5’ to 3’

89
Q

Which of the following events occurs during transcription?

A

A molecule of RNA is formed based on the sequence of nucleotides in DNA.

90
Q

Which of the following is a correct statement about mRNA?

A

mRNA moves from the nucleus to the cytoplasm following RNA processing.

91
Q

The site of translation is

A

ribosomes in the cell cytoplasm.

92
Q

Which one of the following does not play a role in translation?

A

DNA

93
Q

Which of the following does not occur during RNA processing?

A

mRNA attaches to the small subunit of a ribosome.

94
Q

The first step of translation begins when __________.

A

the ribosome binding site (RBS) on the mRNA binds to the 16S rRNA to begin the formation of the initiation complex

95
Q

During the initiation step of translation, the fMet charged tRNA assembles in which site of the ribosome?

A

P site

96
Q

How does the ribosome know if the entering charged tRNA is correct?

A

The anticodon on the tRNA base pairs to the codon on the mRNA.

97
Q

Where would one find an uncharged tRNA molecule in a ribosome?

A

In the P and E sites

98
Q

What kind of bond is formed when two amino acids join together?

A

A peptide bond

99
Q

How is translation terminated?

A

When a protein called a release factor enters and binds to the A site

Immunology & Virology (4 decks)

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