Question

Describe, in terms of ribose ring pucker conformations and hydrogen bonding ability, how the presence of the 2′ hydroxyl group on RNA causes differences in the secondary and/or tertiary structures commonly adopted by RNA compared to DNA

Answer 1

Solution:

The ribose ring in nucleic acid is nonplanar and has conformation that can be defined by the sugar pucker. This usually presents in C2'-endo or C3'-endo conformation.

• C2'-endo sugar pucker cannot be adopted by Ribose in RNA because of steric hindrance between -OH group at C2' and phosphate group on C3'. RNA adopt only C3'-endo form that allow RNA to form a A-type helics and cannot adopt the standard Watson Crick double helical structure.
• RNA can form double helical hairpin, loop structure.
• While DNA sugar pucker can be C2'-endo (B-DNA) or C3'-endo (A-DNA) as deoxyribose lacks oxygen at c2' position.