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Biochem > Nucleotides > Flashcards

Nucleotides Flashcards

1
Q

B form

A

normal form

(watson and crick

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2
Q

A form

A

dehydrated b form

-nucleotide tilted 20 degree relative helical axis

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3
Q

Z form “zig zag”

A

stretches of alternating purine and pyrimidines.

  • base pairs flip 180 degrees
  • left handed helix
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4
Q

Open reading frame

A

long stretch of nucleotides that can encode polypeptide due to absence of stop codons.

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5
Q

DNA requires

A

dNTPs
divalent cation (mg2+)
template dna
primer provides 3’ OH

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6
Q

miRNA

A

small RNA complementary to mRNA that inhibits translation of mRNA

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7
Q

siRNA

A

small RNA that binds to mRNA causing destruction of mRNA

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8
Q

RNA polymerase requires

A 
4 NTPs
divalent cation (Mg2+)
template DNA
-NO primer required
-lacks endo and exo nuclear activity
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9
Q

What is the DNA polymerase Reaction mechanism.

A

5’ to 3’ synthesis

  • nucleophilic attack on alpha phosphate group of dNTP
  • PPi is hydrolyzed to Pi+ Pi
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10
Q

Transcriptional termination

A
  • Rho dependent
  • Rho independent:
  • involves stem loop structure in mRNA.
  • stem loop is followed by UUUs
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11
Q

Prokaryotic mRNA are

A

polycristronic

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12
Q

Eukaryotic mRNA are

A

monocistronic

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13
Q

How are eukaryotic mRNA post transcriptionally modified

A
  • capping: attachment of 7-methlyguansine using 5’ to 5’ triphosphate linkage
  • polyadenylation: attachment of 40 to several hundred adenine nucleoties to 3’ end of mRNA
  • splicing
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14
Q

Aminoacyl-tRNA synthestase

A

attaches amino acid to tRNA

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15
Q

Orientation of Translation

A

ribosomes move 5’ to 3’ along mRNA

-protein is synthesized N to C

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16
Q

Initation of translation

A

assemble and align ribosome, mRNA and tRNA (fMet)

17
Q

What is the exception for genetic code

A

mitochondria genetic code differs from universal code

18
Q

Translational start site

A

prokaryotes use shine delgarno sequence to align ribosome on the mRNA upstream 5’ of AUG
-eukaryotes: use 5’ Cap to align the ribosome on the mRNA

19
Q

WHat is the function of nucleic acids

A
  • building blocks of DNA and RNA
  • transport of chemical energy within the cell (ATP)
  • signal molecule (cyclic AMP)
20
Q

Nucleic Acid

A

linear, non-branched polymer of nucleotides

21
Q

Semiconservative Hypothesis of Meselson and Stahl

A
  • Grew E. coli in 15NH4Cl until DNA was completely labeled.
  • Transferred E. coli to 14NH4Cl containing media.
  • Followed labeling pattern of DNA through several generations using density gradient equilibrium sedimentation
22
Q

What is the spacing in DNA helix

A

3.4 angstrom

23
Q

What is the hypochromic effect

A

DNA can melt and re anneal

Biochem (7 decks)

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