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Bio 323 - Exam Two > PCQ's > Flashcards

PCQ's Flashcards

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1
Q

The affinity of a sequence-specific transcriptional regulator for a DNA sequence can increase if it dimerizes because

A
  • more bases in the DNA can be bound
  • more contacts can be made with the phosphodiester backbone
  • the potential for cooperative binding exists
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2
Q

How are eukaryotic mRNAs processed?

A
  • Capped on the 5’ end
  • Polyadenylated on the 3’ end
  • Internal segments removed by splicing
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3
Q

What parts of a gene are included in a mature mRNA?

A
  • coding (translated) sequence
  • exons
  • noncoding (untranslated) sequence
  • the poly(A) signal (AAUAAA)
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4
Q

What parts of a gene are included in the lariat?

A

Introns

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5
Q

CPSF

A

Binds to the poly(A) signal (AAUAAA) to help specify the 3’ end of an mRNA

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6
Q

CstF

A

Binds to a GU rich signal, helps specify the 3’ end of an mRNA.

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7
Q

PAP

A

adds poly(A) tail to mRNA.

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8
Q

poly(A) binding protein

A

associates with poly(A) tails.

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9
Q

spliceosome

A

Joins exons together.

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10
Q

Alternative splicing can yield mRNAs that differ by the inclusion or exclusion of what?

A

a particular exon

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11
Q

How might alternative splicing yield mRNAs that differ only in the length of a particular exon?

A
  • the use of an alternative 3’ splice site.

- the use of an alternative 5’ splice site.

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12
Q

Enzymes involved in degrading prokaryotic mRNAs are primarily

A

3’->5’ exonucleases

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13
Q

For mRNA-specific regulation of translation and mRNA stability, regulatory proteins or non-coding RNAs bind to particular structures or sequences in target mRNAs. To translationally repress bacterial mRNAs, regulators typically bind _________

A

Shine Dalgarno sequence

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14
Q

For mRNA-specific regulation of translation and mRNA stability, regulatory proteins or non-coding RNAs bind to particular structures or sequences in target mRNAs. To translationally repress eukaryotic mRNAs regulators typically bind_________

A

the 3’ or 5’ UTR

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15
Q

Enzymes involved in degrading eukaryotic mRNAs are

A
  • endonucleases
  • 5’->3’ exonucleases
  • 3’->5’ exonucleases
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16
Q

Although individual mRNAs can be regulated in their translation, translation can also be controlled globally. In eukaryotes, global repression of translation involves:

A
  • accumulation of eIF2 in its inactive, GDP bound form.
  • increased affinity of phosphorylated eIF2 for its GEF (eIF2B).
  • phosphorylation of translation initiation factor eIF2.
  • prevention of eIF2B from being able to function
17
Q

MicroRNAs and siRNAs function by base-pairing with target RNAs. What can cause immediate degradation of the target mRNA?

A

Extensive base-pairing

18
Q

MicroRNAs and siRNAs function by base-pairing with target RNAs.What can cause translational repression, followed by eventual mRNA degradation

A

less extensive base-pairing

19
Q

piRNAs

A
  • newly discovered class of small RNAs
  • can act to silence
    transposons (mobile DNA elements that can hop and in out of genomes)
20
Q

Xist

A

a ncRNA that acts as a scoffold to repress the X chromosome in XX mammals.

21
Q

Splice site usage can be affected by:

A
  • speed of RNA polymerase.
  • chromatin structure.
  • sequences within exons.
  • sequences at the exon-intron and intron-exon boundaries.
22
Q

What catalyzes the transesterification reactions involved in pre-mRNA splicing?

A

non-coding RNAs

23
Q

Recognition of the 5’ splice site and the branch-point site during splicing involves:

A
  • base-pairing by snRNAs to the pre-mRNA

- binding by sequence-specific binding proteins

24
Q

The splicing reaction proceeds as follows

A
  • recognition of the branch-point sequence and 5’ splice site.
  • formation of a lariat, causing separation of the upstream exon from the intron.
  • joining of the upstream and downstream exons.
25
Q

How were the snRNAs discovered?

A

through immunoprecipitation of snRNPs using human autoantibodies

26
Q

Why did the normal serum of Dr. Steitz’s MD/PhD student serve as a good control for the experiments that led to the discovery of snRNAs?

A

it didn’t contain any antibodies against snRNPs

27
Q

What does it mean that the genetic code is a triplet code?

A

Three nucleotides specify one amino acid

28
Q

The fact that the genetic code is degenerate means that:

A
  • Different tRNAs can add the same amino acids

- More than one codon specifies the same amino acid

29
Q

whats required during synthesis of a polypeptide chain in cells (ignoring requirements for the formation of aminoacyl-tRNA and translation initiation)?

A
  • tRNA
  • ribosome
  • rRNA
  • GTP hydrolysis
30
Q

what matches the mRNA codon with the correct amino acid?

A

tRNA

31
Q

what adds an amino acid to tRNA?

A

tRNA synthetase

32
Q

what adds an amino acid to elongate a polypeptide?

A

peptidlytransferase

33
Q

whats the overall direction of ribosome movement on mRNA?

A

5’ to 3’

34
Q

which site is the ribosomal site for new amino-acyl tRNA?

A

A site

35
Q

at which end of the polypeptide are new amino acids are added

A

C-teminis

36
Q

When can a new round of translation initiate?

A

after initiation of the last round

37
Q

Using the following schematic of a short eukaryotic mRNA, identify the major translation product.
(5’- AGGCUUUAACCAUGGUAUGGACCUAAAUAAGUGAAUAUUG-3’)

A

MVWT

Bio 323 - Exam Two (4 decks)

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