Schwabe 2 DNA double helix

Question 1

Covalent bonds:

Answer 1

• Very strong - single & double Short (C–C = 1.54Å), Shared electrons, 85-175 kcal / mol

Question 2

Non-covalent bond:

Electro static interactions:

Answer 2

• Weak to strong c. 1–50 kcal / mol Depend on distance

Depend on dielectric constant “Salt bridge

Question 3

Hydrogen bonds

Answer 3

• Weak 1–5 kcal / mol
Longer than covalent bonds c. 2Å Directional
Donor —– Acceptor : N–H —– N N–H —– O O–H —– N O–H —– O

Question 4

van der Waals interactions (London dispersion forces)

Answer 4

• Weak 0.5–1 kcal / mol

Attraction between induced partial charges

Question 5

Hydrophobic effect

Answer 5

to bury hydrophobic surfaces so they don’t make water ordered

Question 6

Phosphates must be on the outside..

Answer 6

due to negative charge

Question 7

following X ray diffeaction analysis of DNA fibres …

Answer 7

…represents B form of DNA

DNA is right-handed double stranded helix with anti-parallel strands. Reverse polarity to a-helix.

Question 8

DNA helix presents wide (major) & narrow (minor) grooves between dribose-phosphate strands to

Answer 8

… read DNA seq for proteins to petrude into binding withough taking DNA molecule apart

Question 9

Proteins bind to …

Answer 9

wide MAJOR groves

Question 10

supercoiled form is..

Answer 10

…less viscous, more compact

Question 11

hyperchromism

Answer 11

increases absorbance of wavelength

Question 12

ANNEAL / HYBRIDIZE

Answer 12

⇨ can be separated & put together (ANNEAL / HYBRIDIZE) during slow cooling

Question 13

gene sized fragments for HYBRIDIZATION ANALYSIS:

Answer 13

forensically to establish if 2 samples are genetically identical
⇨ relatedness of non-identical samples

Question 14

DNA topoisomerases e.g.

Answer 14

DNA gyrase