2. DNA structure Flashcards
How many turns in B helix?
10
How many turns in A helix?
11
How is DNA B helix defined?
Average structure of DNA in solution
How does A helix differ from B helix?
More compressed, shorter, wider
When is Z helix formed?
Transiently during transcription, also for specific sequences
Which DNA structure does dsRNA commonly adopt?
A helix
Which non-covalent interactions form between bases?
Hydrogen bonds and Van der Waals interactions
What drives helix formation?
The hydrophobic effect
Which parts of the DNA are hydrophobic and hydrophillic?
Bases are hydrophobic, the backbone is hydrophillic
What is the distance between two sugars in the DNA backbone?
6 Angstrom
What is the typical with of a nucleotide base?
3.3 Angstrom
Why do bases stack on top of each other?
Because otherwise there would be a water-filled hole between bases, which is energetically discouraged
Why do bases twist with respect to each other?
To maximise exposure of hydrophillic parts to water and to maximise H-H bonds between bases
Which bases are purines?
A and G
Which bases are pyrimidines?
C and T