Question

During splicing, the exons are joined and the enzyme which catalyzes this reaction is

• A. RNA ligase
• B. RNA catalase
• C. RNA polymerase
• D. RNA primase

Answer 1

Answer: (A)

RNA primase synthesizes RNA primer which is a strand segment (complementary to the template) and has a free 3’ hydroxyl group to facilitate addition of nucleotides by polymerase enzymes. RNA polymerase synthesizes RNA using DNA template strand by adding the ribonucleotides to a primer in 5' to 3' direction via phosphodiester bonds. Splicing is removal of introns from the primary transcript and ligation of exons to form a continuous sequence specifying a functional polypeptide. RNA ligase enzyme joins two exons together via phosphodiester bond between 3’ hydroxyl at the end of one exon and a 5’ phosphate at the end of another exon.