Splicing
(I)occurs in the cytosol.
(II)results from 2' -OH on the exon attack on the 5' splice site.
(III)is completed when the 3' -OH on the newly cut exon attacks the 5'-terminal phosphate on the next exon.
A)I,II
B)I,III
C)I only
D)II only
E)III only

Question

Quizplus · Accepted Answer

Splicing occurs in the nucleus, not the cytosol, making statement I incorrect. The mechanism of splicing involves the 2' -OH group of an adenine within the intron attacking the 5' splice site to form a lariat structure, not the 2'-OH on the exon as stated in II. The correct mechanism is described in III, where the 3' -OH of the upstream exon attacks the 5' phosphate of the downstream exon, ligating the two exons together and releasing the intron lariat.

Splicing (I)occurs in the Cytosol