DNA Flashcards
Purine
Adenine and Guanine (2 raangs)
-Guanine has the most H+ donors/acceptors (6) while Adenine (5)
Pyrimdine
Uracil, Thymine and Cytosine
Nucleotide
- Sugar 2. Phosphate 3. Nitrogenous base
Ribose
2’ 3’ OH down
Deoxyribose
2’ OH is absent in ribose
What link connects a nucleotide w a ribose?
B-glycosidic link
What linke connects to successive sugar molecules in a polynucleotide?
Phosphodiester bond (broken by phosphodiesterase)
Hydrogen bonding w BPs
G triple bonds with C= 3 hydrogen bonds
A double bonds with T = 2 hydrogen bonds
How many BP per turn of helix?
10 BP per turn of the helix
DNA strands
3’ –> 5’ Template, Coding strand
5’–> 3’ Non-template strand
Start Codons
AUG
Stop Codons
U Are Annoying (UAA)
U Are Gone (UAG)
U Go Away (UGA)
DNA Transcription (basic steps)
1) Initiation 2) Elongation 3) Termination
RNA polymerase 1
only bacteria, contains 4 subunits + sigma subunit, makes rRNA
RNA polymerase 2
Eukaryotes, involved in mRNA synthesis
RNA polymerase 3
Transcribes rRNA and tRNA
Rate of elongation in eukaryotes
40 nucleotides/second in eukaryotes
Hairpin Loop
G—C rich, hairpin loop forms from inverted repeats in DNA lead to the end of transcription, signals RNA to fall off (Rho-independent)
How many AA per turn of helix?
3.5 AA per turn of the alpha helix
Histones
small proteins used to wrap DNA into chromatin, mostly + charged so its attacked to a (-) charged DNA backbone.
OCTAMER: H2A, H2B, H3, H4 X 2
Euchromatin vs Heterochromatin
less dense DNA= euc
tightly packed DNA= hetero
