Mastering Biology Question: Not letting me upload screenshot. However, question
ID: 161829 • Letter: M
Question
Mastering Biology Question:
Not letting me upload screenshot. However, question is:
Compare and contrast the mechanisms of self-splicing by group I and group II introns.
Sort these {items} below into the proper categories (Categories are Group I introns, Group II introns, Both Group I and Group II introns)
lariat forms
no lariat forms
the mechanism involves the binding of a free guanine nucleotide in the fold of the intron
do(es) not require the spliceosome
the mechanism involves steps similar to the spliceosome-dependent splicing
act(s) as catalytic RNAs that self-splice
Explanation / Answer
Group-I & II introns are self-splicing in nature, that means they possess enzymatic activity and catalyses their splicing during RNA processing. So Group-I & II introns are considered as Ribozymes. Group-I introns are found in some nuclear pre-rRNA genes and Some organelle genes, where as Group-II introns are found in primary transcripts of Organellar genes. These two introns are distinguished by their mechanisms splicing & also their structure. Durng splicing they perform two consequitive transesterification reactions.
Group-I introns mechanism: 1. Attack of 5' splice site by 3' GMP/GDP/GTP & perform first transesterification reaction. Due to this 5' exon released. 2. The released exon 3' end attacks 3' end of intron leads to release of intron and joining of exons. There is no lariate formation. These two steps are reversable in nature.
Unlike group-I introns, Group-II introns utilise internal energy to perform the splicing steps and in first step it utilizes ATP instead of GTP for attack of 2' oH group. In this case lariate structure formation takes place.
Group-I: No lariat forms; The mechanism involves the binding of a free guanine nucleotide in the fold of the intron do(es) not require the spliceosome
Group-II: Lariat forms; The mechanism involves steps similar to the spliceosome-dependent splicing
act(s) as catalytic RNAs that self-splice