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Mini 2 > Sands > Flashcards

Sands Flashcards

1
Q

What does the antiparallel nature of double-stranded DNA mean?

A

The two strands run from 5’ to 3’ in opposite directions.

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2
Q

While studying the structure of a small gene that was recently sequenced during the
Human Genome Project, an investigator notices that one strand of the DNA molecule
contains 20 A’s, 25 G’s, 30 C’s, and 22 T’s. How many of each base is found in the
complete double-stranded molecule?

A

A=42, G=55, C=55, T= 42

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3
Q

The extent of DNA synthesis in a cell could most specifically be determined by
measuring the incorporation of which of the following radiolabeled compounds?

A

Thymine

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4
Q

DNA contains which one of the following components?

A

Negatively charged phosphate groups on the exterior of the molecule

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5
Q

If a completely radioactive double-stranded DNA molecule undergoes two rounds of
replication in a solution free of radioactive label, what is the radioactivity status of the
resulting four double-stranded DNA molecules?

A

Half should contain no radioactivity

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6
Q

During which phase of the cell cycle is DNA replicated?

A

S

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7
Q

The sequence of part of a DNA strand is the following –ATTCGATTGCCCACGT-.
When this strand is used as a template for DNA synthesis, the product will be which one of
the following?

A

ACGTGGGCAATCGAAT

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8
Q

The isolation of nascent Okazaki fragments during DNA replication led to the surprising
discovery of uracil in the fragment. The uracil is present due to which of the following?

A

The need for a primer

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9
Q

Which of the following is true about the lagging strand?

A

It is synthesized as a series of Okazaki fragments.

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10
Q

What is a replication fork?

A

An area where the DNA separates into two strands and DNA synthesis occurs.

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11
Q

If a 1,000-kilobase fragment of DNA has 10 evenly spaced and symmetric replication origins and DNA polymerase moves at 1 kilobase per second, how many seconds will it take to produce two daughter molecules (ignore potential problems at the ends of this linear piece of DNA)? Assume that the 10 origins are evenly spaced from each other, but not from the ends of the chromosome.

A

D) 50

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12
Q

Which of the following enable all the DNA of a eukaryote to be replicated in 8 hours.

A

There are multiple origins of replication.

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13
Q

Which of the following is necessary for DNA polymerase to polymerize deoxynucleotides?

A

3’-hydroxyl group

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14
Q

Analysis of a cell line that rapidly transforms into a tumor cell line demonstrated an increased mutation rate within the cell. Further analysis indicated that there was a mutation in the DNA polymerase enzyme that synthesizes the leading strand. This inactivating mutation is likely to be in which of the following activities of this DNA polymerase?

A

3’-5’ exonuclease activity

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15
Q

Why is DNA synthesized only in a 5’ to 3’ direction?

A

It has to do with proof reading.

-and because the phosphate group is on the 5’end

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16
Q

DNA polymerase , the eukaryotic primase, differs from DNA polymerase  by which of the following?

A

Does not contain 3’ to 5’ exonuclease activity

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17
Q

Which of the following enzymes are responsible for this chemical reaction? 5’-AACGGGATCCATTGCTA-3’ 5’-AACGGGATCCATTGCTA-3’ 3’-TTGCCCTAGGTAACGAT-5’ 3’-TTGCCCTAGGTAACGAT-5’

A

DNA polymerase

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18
Q

What is the polymerase that generates the primer in eukaryotes called

A

DNA polymerase α

-alpha

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19
Q

DNA polymerase δ - delta

A

Lagging

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20
Q

DNA polymerase ε

A

leading

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21
Q

DNA polymerase β

A

DNA repair

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22
Q

DNA polymerase α

A

primase in eukaryotes

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23
Q

Primase is not required during DNA repair processes because of which of the following?

A

DNA polymerase  delta and epsilon can use any 3’-OH for elongation.

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24
Q

During DNA replication, which type of enzyme separates double-stranded DNA into the single-stranded DNA that is needed as a template for the DNA polymerases?

A

Helicase

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25
Q

Which of the following keeps the DNA polymerase on the DNA?

A

PCNA -binding clamp

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26
Q

What enzyme is necessary to seals the phosphodiester backbone and fuse Okazaki fragments together?

A

Ligase

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27
Q

What kind of enzyme is telomerase?

A

A RNA-dependent DNA polymerase

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28
Q

A genetic engineer announces the birth of a baby with an artificial chromosome that carries an extra copy of the gene for telomerase. The gene is engineered with an inducible promoter that causes transcription in response to the insect hormone ecdysone. Why should people with this artificial chromosome want to take ecdysone pills?

A

To delay aging

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29
Q

Telomeres are complexes of DNA and protein that protect the ends of linear chromosomes. In most human somatic cells, telomeres shorten with each division. In stem cells and in cancer cells, however, telomeric length is maintained. Which of the following statements is true about how telomerase functions?

A

Telomerase provides both the RNA and the polymerase needed for synthesis.

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30
Q

The following four items are involved in the initiation of transcription. Which of the following four is composed of DNA?

A

TATA box

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31
Q

A four-year-old child who becomes easily tired and has trouble walking is diagnosed with Duchenne muscular dystrophy, an X-linked recessive disorder. Genetic analysis shows that the patient’s gene for the muscle protein dystrophin contains a mutation in the promoter region. What would be the most likely effect of this mutation?

A

Initiation of dystrophin transcription will be lacking.

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32
Q

The 5’ UTR contains which of the following?

A

The mRNA cap

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33
Q

Which of the following codons is the start codon?

A

AUG

34
Q

A gene encodes a protein with 150 amino acids. There is one intron of 1,000 bp, a 5’- untranslated region of 100 bp, and a 3’-untranslated region of 200 bp. In the final processed mRNA, how many bases lie between the start AUG codon (include the start codon) and the final termination codon?

A

450

35
Q

Which of the following nucleotide sequences is never found in an exon?

A

promoter

36
Q

Splicing best refers to which of the following statements?

A

The removal of introns from transcripts

37
Q

The codon UAA is referred to as a stop codon. What exactly is a stop codon?

A

The stop codon instructs the translation machinery to stop the process of translation.

38
Q

What does a stop codon interact with that causes translation to cease?

A

Release factors: Stop codons interact with proteins that are called release factors. The release factors’ tertiary structure is similar to the tertiary structure of a tRNA. This allows release factors to fit into the “slot” that a tRNA would fit into. The release factors interact with the stop codon to cause all the translation components to “come apart” and thereby stop translation.

39
Q

The 3’ UTR contains which of the following nucleotide sequences?

A

The polyadenylation sequence

40
Q

A patient is shown to have a deletion of 500 base pairs within the 3.7 kilo-base-pair sequence between the promoter of the L-type pyruvate kinase (PK) gene and an upstream erythroid-cell-specific enhancer element for the PK gene. What is the most likely outcome of the mutation in erythroid cells?

A

There will be no change in the rate of enzyme synthesis.
-Enhancers are position and orientation independent. So, deleting 500 bp from a 3,700 basepair region should simply bring the enhancer slightly closer to the promoter that it is activating and not change the transcription stimulation of the RNA polymerase much, if at all.

41
Q

The hypothetical “stimulin” gene contains two exons that encode a protein of 100 amino acids. They are separated by an intron of 100 bp beginning after the codon for amino acid 10. Stimulin messenger RNA (mRNA) has 5’ and 3’ untranslated regions of 70 and 30 nucleotides, respectively. The poly A tail is 100 nucleotides in length. A complementary DNA (cDNA) made from mature stimulin RNA would have which of the following sizes?

A

500 bp
100 codons x 3 nucleotides/codon = 300 nucleotides, the 5’ UTR (70 nucleotides), the 3’ UTR (30 nucleotides) and the poly A tail (100 nucleotides). All these nucleotides adds up to 300 + 70 + 30 + 100 = 500 nucleotides.

42
Q

What coordinates transcription with pre-mRNA processing?

A

The C-terminal domain of RNA pol II

43
Q

Eukaryotic mRNA molecules are processed and modified prior to transport out of the nucleus. Which of the follow modifications are involved in processing mRNA?

A

Capping

44
Q

Which of the following are true about the so-called caps of RNA molecules?

A

They are necessary for the ribosome to find the 5’ end of the mRNA.

45
Q

The removal of introns and subsequent self-splicing of adjacent exons occurs in some portions of primary ribosomal RNA transcripts. How does the splicing of introns in messenger RNA precursors occur?

A

The process is carried out by spliceosomes.

46
Q

A 2-year-old boy has required frequent transfusions throughout his life because of anemia. A peripheral blood smear demonstrates microcytic, hypochromic red blood cells, with target cells
and anisopoikilocytosis. After further genetic testing, the child’s spleen is removed to lessen the need for transfusions. When his genetic code is sequenced, the following mutation is seen at the 5’ end of one of his introns. This change is most likely to affect which of the following processes?

A

**picture of DNA segments

splicing

47
Q

A geneticist introduces the genes for a super-spliceosome into the human germ line that is able to remove every intron without fail. In which way would people with this genetic innovation differ from the rest of the species?

A

They would produce fewer unique proteins.

48
Q

A one-year-old boy with chronic anemia is found to have -thalassemia. Genetic analysis shows that one of the -globin genes has a G to A mutation that creates a new splice acceptor site nineteen nucleotides upstream from the normal splice acceptor site of the first intron. Which
of the following best describes the new messenger RNA molecule that can be produced from this mutant gene?

A

exon 2 will be to long

49
Q

What is the best explanation for what the point mutation has done?

A

Abolishes a splice site

–normal DNA picture with the affected below with 2 different strands

50
Q

DNA of the ovalbumin gene is denatured and allowed to hybridize with mature processed mRNA isolated from cells expressing ovalbumin. Electron microscopy revealed heteroduplex molecules like the one shown in the figure. What does the unpaired segment at the right end of the shorter/thinner strand of the heteroduplex represent?

A

3’ end of the mRNA

51
Q

The 5’ cap and the 3’ poly-A tail are added in the production of mature eukaryotic mRNA.
The 5’ cap and the 3’ poly-A tail have which respective functions?

A

Translation initiation and transcript stability

52
Q

A mutation to which of the following nucleotide sequences in eukaryotic mRNA will affect
the process by which the 3’-end poly-A tail is added to the mRNA.

A

The polyadenylation signal sequence is found in the 3’ UTR. It’s sequence is AAUAAA.

53
Q

In the read-out of the genetic code in eukaryotes, which one of the following processes acts before any of the others?

A

Termination of transcription

54
Q

The genetic code is said to be degenerate because of which of the following?

A

Many of the amino acids have more than one triplet codon.

55
Q

The reason there are 64 possible codons is which of the follow?

A

There are four possible bases at each of three codon positions.

56
Q

Which of the following statements are true about the genetic code?

A

No signal exists to indicate the end of one codon and the beginning of another

57
Q

Under conditions where methionine must be the first amino acid, what protein would be coded for by the following mRNA?
5’-CCUCAU AUG CGC CAU UAU AAG UGA CACACA-3’

A

Met-Arg-His-Tyr-Lys

58
Q

What is the consequence of this mutation? G A T T C A T G T T C G G A C T G G T G T A T G A T T C A T G T T C G G A C T G T A T

The following mutation occurred near the 5’ end of the coding sequence. The sequence shown is the coding strand of the gene. It includes the start codon and the mutation.

A

A single amino acid is missing in the sequence

59
Q

The peptide bond formed between 2 adjacent amino acids is formed by what kind of
catalytic reaction?

A

An acid-base reaction

60
Q

The peptide bond formed between 2 adjacent amino acids is formed by what?

A

The 28 S rRNA is the catalyst for this reaction.

61
Q

A patient displays tiredness and lethargy, and blood work demonstrates an anemia. Western blot analysis indicates significantly greater levels of -globin than -globin. Molecular analysis
indicates a single nucleotide change in an intron of the -globin gene. How does such a mutation lead to this clinical finding?

A

Creation of an alternative splice site, such that -globin levels are decreased.

62
Q

Ferritin

A

cytosolic iron binding protein expressed when iron is abundant in the
cell.

63
Q

Transferrin receptor

A

a plasma
membrane receptor important for the
import of iron into the cytosol.

64
Q

In eukaryotes, to what does cycloheximide bind to inhibit the peptidyl transferase reaction?

A

The 60S ribosomal subunit

65
Q

The pediatrician, in addition to rushing the child to the hospital, prescribes a drug that blocks prokaryotic peptide bond formation, even though it can have serious side effects. That drug is which of the following?

A

Chloramphenicol

66
Q

Of what is the peptidyl transferase enzyme composed?

A

. rRNA

67
Q

what does not have an ATP or GTP requirement?

A

Formation of the peptide bond during protein synthesis

68
Q

A 30-year-old man who is vomiting, has bloody diarrhea, is dehydrated, and is delirious, is brought to the emergency department. The attending physician is told that he is an amateur chef who was trying out a new creation in which he wanted to experiment with the extracts of castor beans. This person’s symptoms are all due to which of the following?

A

Ribosomal inactivation by covalent modification-ricin

69
Q

Under conditions of active exercise, protein synthesis is reduced in the muscle. Under these conditions, which aspect of translation is inhibited?

A

Elongate during translation

70
Q

whats true about the regulation of ferritin and the transferrin receptor?

A

Ferritin has a regulatory element in its 5’ UTR.

71
Q

A hypothetical patient was suffering from excessive free iron in the blood, yet a cellular analysis indicated low intracellular levels of iron, despite high intracellular levels of ferritin, and normal transferrin levels in the blood. The disease was shown to be caused by a single base change in the DNA that led to a dysfunctional protein. The mutation is likely to be in which of the following proteins?

A

Aconitase

72
Q

diptheria.

A

The diptheria toxin ribosylates eEF2 by using NAD+ to add most of the nicotine-adenine dinucleotide to a modified histidine amino acid that is essential for eEF2 to interact with the ribosome and effect translocation.

73
Q

post-translational modifications is most frequently used to rapidly alter protein function?

A

Phosphorylation

74
Q

Diphtheria toxin is produced by the gram positive bacilli Corynebacterium diphtheria. The toxin ribosylates eEF2. What is the effect of this modification?

A

The newly formed peptidyl tRNA cannot move to the P site.

75
Q

When the polio virus enters a cell, it takes over the cell’s translational machinery by cleaving which of the following?

A

eIF4G

76
Q

The small ribosomal subunit of eukaryotes contains which of the following rRNAs?

A

18

77
Q

Which of the following is a difference between RNA and DNA?

A

RNA contains ribose instead of 2-deoxyribose

78
Q

Amanita phalloides, the death-cap mushroom. Care is supportive. A major toxin of the death-cap mushroom is the hepatotoxic octapeptide alpha-amanitin. This toxin inhibits which of the following?

A

RNA polymerase

79
Q

WHAT is true about RNA polymerases but not true about DNA polymerases?

A

They can initiate synthesis of their polynucleotide product.

80
Q

How are most of the rRNAs synthesized in the cell?

A

The larger rRNAs are synthesized as a unit by RNA pol I and then processed.

81
Q

What is the nucleotide sequence that is added to the 3’ end of every tRNA?

A

5’-CCA-3’

82
Q

WHAT are true about the so-called caps of RNA molecules?

A

They are necessary for the ribosome to find the 5’ end of the mRNA

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