Which introns are self-splicing?
Self-splicing occurs for rare introns that form a ribozyme, performing the functions of the spliceosome by RNA alone. There are three kinds of self-splicing introns, Group I, Group II and Group III. Group I and II introns perform splicing similar to the spliceosome without requiring any protein.
What is the difference between group 1 and group 2 introns?
The key difference between group I and group II introns is that in group I introns, the splicing reaction is initiated by a guanosine cofactor, while in group II introns, the splicing reaction is initiated by internal adenosine. RNA splicing or pre-mRNA splicing is one such post-transcriptional modification.
What is the major difference between group 1 and 2 self-splicing reactions?
Question: What is the major difference between Group 1 and Group 2 self-splicing reactions? Group 1 involves nucleophilic attack from a 3’OH of a free GTP. Group 2 uses a 2’OH of a nucleotide contained within the intron. Group 1 involves nucleophilic attack from a 2’OH of a nucleotide contained within the intron.
Who discovered self-splicing introns?
In an elegant series of studies of this splicing reaction, Thomas Cech and his coworkers established that the RNA spliced itself to precisely excise the 414-nucleotide intron.
What are group II introns?
Group II introns are a large class of self-catalytic ribozymes and mobile genetic elements found within the genes of all three domains of life. Ribozyme activity (e.g., self-splicing) can occur under high-salt conditions in vitro.
What is intron splicing Group 1?
Group I introns are large self-splicing ribozymes. They catalyze their own excision from mRNA, tRNA and rRNA precursors in a wide range of organisms. The core secondary structure consists of nine paired regions (P1-P9). Group I introns often have long open reading frames inserted in loop regions.
What is a difference between group I and group II introns quizlet?
-Group I introns are found across all organisms, including vertebrates. -Group II introns use an exogenous guanosine as a cofactor.
What are Spliceosomal introns?
Spliceosomal introns, which have been found in most eukaryotic genes, are non-coding sequences excised from pre-mRNAs by a special complex called spliceosome during mRNA splicing. Introns occur in both protein- and RNA-coding genes and can be found in coding and untranslated gene regions.
Where are group II introns found?
Distribution and phylogeny Group II introns are found in rRNA, tRNA, and mRNA of organelles (chloroplasts and mitochondria) in fungi, plants, and protists, and also in mRNA in bacteria.
Where are introns found?
Introns are found in the genes of most organisms and many viruses and can be located in a wide range of genes, including those that generate proteins, ribosomal RNA (rRNA) and transfer RNA (tRNA).
How are Group 2 introns removed?
Group II introns are mobile ribozymes that self-splice from precursor RNAs to yield excised intron lariat RNAs, which then invade new genomic DNA sites by reverse splicing.
Why do helicase and gyrase need to work together to keep the replication fork moving forward?
Why do helicase and gyrase need to work together? Helicase unwinds DNA and gyrase relieves the torsional strain. Match the name of the DNA repair mechanism with the correct description. Functions with DNA replication to remove incorrect nucleotides from the nascent strand.
How is the splicing of a group I intron performed?
Catalysis. Splicing of group I introns is processed by two sequential transesterification reactions. The exogenous guanosine or guanosine nucleotide ( exoG) first docks onto the active G-binding site located in P7, and its 3′-OH is aligned to attack the phosphodiester bond at the 5′ splice site located in P1,…
What is the role of Group II introns?
Splicing by group II introns plays a major role in the metabolism of plants, fungi, and yeast Group II introns are large, autocatalytic ribozymes that catalyze RNA splicing and retrotransposition. Splicing by group II introns plays a major role in the metabolism of plants, fungi, and yeast
Where does splicing take place in a nuclear gene?
During splicing, introns (non-coding regions) are removed and exons (coding regions) are joined together. For nuclear-encoded genes, splicing takes place within the nucleus either during or immediately after transcription.
What causes the folding of Group I introns?
Nevertheless, folding of group I introns in vitro encounters both thermodynamic and kinetic challenges. A few RNA binding proteins and chaperones have been shown to promote the folding of group I introns in vitro and in bacteria by stabilizing the native intermediates, and by destabilizing the non-native structures, respectively.