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Bio 423 > Exam 3 Quiz Questions > Flashcards

Exam 3 Quiz Questions Flashcards

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1
Q

Why is ribosomal RNA not spliced as it is processed?

A

Splicing rejoins RNA after introns are removed

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2
Q

Which posttranslational modification don’t normally increase the stability of mRNAs?

  • 5’ methyl G cap
  • splicing
  • polyA tail
  • uracil
A

Uracil addition

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3
Q

Which is not true about pseudouridylation?

  • Box H/ACA direct pseudouridylation by directly basepairing with the target RNA.
  • tRNAs are pseudouridylated
  • Pseudouridylation decreases the basepairing with adenine
  • Proteins direct the pseudouridylation
A

Pseudouridylation decreases the basepairing with adenine

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4
Q

MicroRNAs

  • are ribozymes
  • basepair to mRNA to direct methyltion
  • basepair to mRNA to direct cleavage
  • basepair ot introns to direct splicing
A

Basepair to mRNA to direct cleavage

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5
Q

What is one reason not contributing to the high rate of retrovirus mutations?

  • DNA-dependent DNA synthesis is error prone
  • Deamination nucleotides in the RNA genome escape repair
  • Retroviruses can cause cancer and cancer is mutagenic
  • Polypeptides are cleaved with proteases
A

Retroviruses can cause cancer and cancer is mutagenic

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6
Q

What is not true about telomerase?

  • They contain the RNA sequences called box H/ACA
  • The 5’ end of the hTERT serves as the RNA template to extend telomeres
  • Telomerase extends the 3’ end of DNA
  • Telomerase synthesized both strands of the telomeric DNA
A

Telomerase synthesized both strands of the telomeric DNA

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7
Q

What is not true about ribosomes?

  • levels change during different rates of growth
  • they are composed of protein and rRNA assembled in the th enucleolus cotranscriptionally
  • they are posttranscriptionally modified by box C/D and H/ACA snoRNAs
  • all are true
A

All are true

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8
Q

RNA editing:

  • changed the codon to a stop codon or to a different codon
  • increases genetic diversity without changes to the DNA sequence
  • can include deamination fo nucleotides
  • all of these
A

All of these

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9
Q

Which step in splicing needs to occur before the spliceosome is considered active?

  • the lariat forms
  • U1 snRNP disassociates
  • the branch site cleaves the 5’ slice site
  • ATP is cleaved
  • all of these
A

U1 snRNP disassociates

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10
Q

The canonical start codon is …

A

AUG

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11
Q

Selenocysteine is a nongenetically encoded amino acid. How is it incorporated into proteins?

A

A serine charged on a tRNA with a codon that recognizes a stop codon is converted enzymatically to selenocysteine.

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12
Q

Deamination of cytosine to ……..

A

uracil

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13
Q

If I is in the 5’ end of the anticodon on the tRNA then it will…

A

basepair with A, U, and C

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14
Q

IF1 is analagous to eIF1A because they both…

A

bind the A site in the ribosome

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15
Q

As elongation continues in prokaryotes, EF-G…

A

Moves into the A site as the growinf peptide chain moves to the P site.

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16
Q

Which is not considered a posttranslational modification?

  • phosphorylation
  • methylation
  • farnesylation
  • pyrolysine
A

Pyrolysine

17
Q

Glycosylation of proteins…

A

… occurs as proteins are translated directly into the ER.

18
Q

In bacteria, regulatabel genes tend to be regulated by…

A

… sigmaS

19
Q

In bacteria, regulatable genes tend to…

A

… have activators that bind enhancers.

20
Q

The Lac repressor…

A

… physically blocks RNA polymerase from binding to the spot.

21
Q

DNA binding proteins bind DNA by…

A

…using free carboxyl and amino groups in amino acid’s R group to hydrogen bond hydrogen and carbons of bases.

22
Q

Attenuation of the Trp operon transcription uses a similar mechanism to…

A

… rho-independent termination of transcription (forms a hairpin loop)

23
Q

The SOS operon is different from the Lac ans Trp operon because…

  • it responds to DNA damage rather than presence or absence of a metabolite
  • the transcriptional represssor is cleaved when SOS response is activated
  • extended SOS response can kill the cell because latent viruses are reactivated
  • all of the above
A

all of the above

24
Q

The RPG operon is different from Lac, Trp, and SOS operon because…

A

… the protein product binds their own transcript, inhibiting transcription

25
Q

The structure that riboswitches take…

A

… is regulated by the type of metabolite that it binds which usually turns off expression of genes that make that metabolite.

26
Q

Recombination can move genes in different orientations. In Salmonella, it uses phase variation to…

A

…increase the phenotypic variation of flagella to evade the host immune system.

27
Q

Lumafactor was developed to treat the F508del mutation in CFTR. Lumafactor does this by…

A

… helping in processing of CFTR.

28
Q

How does the reduced glycosylation of CFTR casue cystic fibrosis?

A

when CFTR is misfolded N-linked glycosylation is reduced and trafficing from the ER to cell membrane does not happen and the protein is degraded.

29
Q

Chromatin remodelers…

A

… slide histones around the DNA

30
Q

Histone posttranslational modifications are mostly…

A

reversible

31
Q

Folate regulates the expression of the Agouti gene by…

A

methylating and silencing the upstream gene of Agouti and permitting expression of Agouti

32
Q

Histone code:

A
  • references to the different protein coding sequences of histones
  • references to specific sequences that tend to be occupied by histones
  • specific combinations of histon PTMs that regulate gene expression
33
Q

Eukaryotic gene regulation varies from prokaryotic because prokaryotes…

A

… use different sigma factors to positively regulate transcription.

34
Q

Hormones such as estrogen induce transcription by…

A

… binding to DNA-binding proteins to induce dimerization and then bind to promoters.

Bio 423 (1 decks)

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