Chapter 3 - Nucleic Acids Flashcards
What does nucleosides lack?
Phosphates
Monomeric units with phosphates
Nucleotides
What are the two purine bases?
Adenine & Guanine (in both DNA and RNA)
What are the three pyrimidine bases?
Cytosine (in both DNA and RNA),
Thymine (in DNA)
Uracil (in RNA)
Where is the glycosidic bond of purines and pyrimidines?
Purines attached at N9 to sugar at C1’
Pyrimidines attached at N1 to sugar at C1’
What substrates do DNA and RNA synthesis require?
dNTP & NTP substrates
Nucleotides are linked through what kind of bond?
Phosphodiester bonds (between the 3’ and 5’ hydroxyl groups) to form long polymers
Reactive nucleoside triphosphates (dNTP’s or NTP’s) are added to growing polynucleotide chain at what end?
3’ end
List the Chargaff’s rules
- All tissues in the same species have the same % of all 4 nucleotides
- % of purines = % of pyrimidines
- %A = %T and %G = %C
What’s the bond between A & T?
2 H bonds
What’s the bond between C & G?
3 H bonds, which is stronger than the bond between A & T
What is double helix stabilized by?
- Hydrophobic interactions: base stacking
- H-bonding between bases purinepyrimidine
- Cations: neutralize the (-) charge on phosphates along the helix of DNA
Which kind of DNA forms under dehydrated, non-physiological conditions; right-handed helix
A form DNA (A-DNA)
Which kind of DNA forms when fully hydrated and under conditions in vivo; right-handed helix; majority of proteins recognize major groove
B-DNA
Found in G-C rich DNA sequences; left-handed helix; may be important in protein recognition & gene regulation
Z-DNA
