Nucleic Acids Flashcards Preview

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Flashcards in Nucleic Acids Deck (20):
1

Pyrimidine tautomers

Predominant: amino
Rare: imino

2

Purine tautomers

Predominant: lactam (keto)
Rare: lactim (enol)

3

Purine numbering

Numbering starts at N on big ring farthest away from little ring and goes to top of big ring (1-6)
Numbering continues at top N of little ring and ends at last N (7-9)

4

Pyrimidine numbering

Numbering begins at bottommost N
#2 position is C double bonded to O
Numbering continues from there

5

Directionality of DNA sequences

5' -> 3'

6

# of H-bonds between A and T

2 H-bonds

7

# of H-bonds between G and C

3 H-bonds

8

4 ways that structure of DNA's double helix is stabilized

1. Pi-stacking interactions between successive base pairs on each rung of ladder
2. H-bonding between bases in a base pair
3. Hydrophobic bases in the middle of the helix and hydrophilic sugar-phosphate backbone on the outside of the helix
4. Electrostatic repulsion between proximal anionic phosphates is stabilized by cations and assorted proteins

9

Melting temperature (Tm)

Temperature at which 50% of DNA has denatured

10

4 types of cellular RNA

1. Ribosomal RNA (rRNA)
2. Transfer RNA (tRNA)
3. Messenger RNA (mRNA)
4. Small RNA (s_RNA)

11

Ribosomal RNA

Integral part of ribosomes and protein synthesis

12

Transfer RNA

Activator and carrier of amino acid residues during protein synthesis

13

Messenger RNA

Product of transcription
Carries information in the genetic code from the nucleus to the cytosol for translation

14

Small RNA

Several types exist and have functions ranging from catalytic activity (ribozymes) and RNA modification

15

Histone octamer

Made up of 2 of each histone subunit: H2A, H2B, H3, H4

16

Histone H1

Helps hold chromatin onto histone octamer

17

Both exonucleases and endonucleases can cleave what end(s) of the phosphodiester bond?

5' and 3' ends can be cleaved

18

RNases

Catalyze 5' phosphodiester cleavage of RNA after 5'->3' pyrimidine nucleotide residues

19

3 ionic residues of RNAse active site

His-12
His-119
Lys-41

20

Restriction endonuclease selectivity

Specific sequences of DNA, which are typically palindromic sequences (symmetrical)