BCEM 393: Nucleic Acids - Structure Quiz 5

BCEM 393 UofC

Deoxyribose (4)

• Furanose structure

• DNA lacks 2’ hydroxyl group; instead has H

• In terms of groups going down from 1’: H - H - OH - H

• 5’ C goes up and has OH on leftside

Backbone of DNA (2)

• Sugars are linked by phosphodiester bridges between the 3’ OH of one sugar and the 5’ OH of an adjacent sugar

• OH groups participate in the bond (become O)

Ribose

• Furanose structure

• RNA has 2’ hydroxyl group

• In terms of groups going down from 1’: H - OH - OH - H

• 5’ C goes up and has OH on leftside

Backbone of RNA (2)

• Sugars are linked by phosphodiester bridges between the 3’ OH of one sugar and the 5’ OH of an adjacent sugar

• OH groups participate in the bond (become O)

Purine (2)

• Common six-membered ring fused to imidazole

• Changes to purine bases only occur on the common six-membered ring

• 4 DBs to draw

• Ns at 1, 3, 7, 9

• N9 is NH

Adenine

• NH₂ group on position 6

Guanine (3)

• Double-bonded O on position 6

• Double bond gone between positions 1 and 6 (N becomes NH)

• NH₂ on position 2

Pyrimidine (2)

• Same common six-membered ring

• All pyrimidines have NH at position 1 and no double bond between positions 1 and 2

• All pyrimidines have double bonded O at position 2

Cytosine (2)

• NH₂ at position 4

Uracil (3)

• No double bond between positions 3 and 4

• Double bonded O at position 4

• NH₂ at position 3

Thymine

• Same as uracil but CH₃ at position 5

Watson-Crick Base Pairing: GC

Watson-Crick Base Pairing: AT