3'

3' - also pronounced 3 prime. The prime numbers comes from which carbon on the sucker part of the base, the attachment is made. 5 prime means that the connection is made on the fifth carbon and 3 prime means that connection is made on the third carbon. It is also used to state reading direction in RNA. 

[[File:5 prime 3 prime.png|600px|right]]

Teaching about 3'