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Nucleotides & Nucleic Acids. Watson & Crick 1953 (Franklin & Wilkins too) Franklin & Wilkins. Heavy bands - indicates recurring bases. X - indicates helical structure. Nucleotides & Nucleic Acids. Watson & Crick 1953 (Franklin & Wilkins too) Watson & Crick Used x-ray crystallography data - PowerPoint PPT Presentation
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Nucleotides & Nucleic Acids
Watson & Crick 1953 (Franklin & Wilkins too)
Franklin & Wilkins
X - indicates helical structure
Heavy bands - indicates recurring bases
Nucleotides & Nucleic Acids
Watson & Crick 1953 (Franklin & Wilkins too)
Watson & CrickUsed x-ray crystallography dataUsed Chargaff’s rules3D structure of DNA, strands antiparallel
Nucleotides & Nucleic Acids
DNA structureComplementarityStrands not identical in base sequence or composition
DNA replication
Nucleotides & Nucleic Acids
DNA structure - different forms
A-DNA B-DNA
Z-DNA
Nucleotides & Nucleic Acids
DNA structure - different forms
Structuretype
A
B
Z
Pitch (Å)
28.2
33.8
45
Axial rise (h) per nt (Å)
2.56
3.38
3.7
Groove width (Å)
minor major 11 2.7
5.7 11.7
8.8 2
Groove depth (Å)
minor major 2.8 13.5
7.5 8.5
3.7 13.8
axial rise (h)distance between bp
Pitch = axial rise x repeat (bp/turn) distance for complete turn of helix So for A-DNA 2.56 Å x 11 bp/turn = 28.2 Å
Z-DNA virtually no major groove due to syn-G, pulls C into major grv
purine rotatedinto major groove
A-DNA A-DNA + bulgeB-DNA
32˚
tilt
ed u
pw
ard
Triple HelixIntrastrand base pairing
Triple Helix using a third strand of DNAInterstrand base pairing
Restriction endonuclease