Practice question

Branch site consensus in budding yeast Saccharomyces cerevisiae is invariant UACUAAC where central adenosine is nucleophile forming two prime-five prime linkage, highly conserved due to need for base pairing with U2 snRNA GUAGUA and recognition by splicing factors. Mammalian branch point consensus is more degenerate YNYYRAY, specifically CURAY motif where R is purine, Y is pyrimidine, containing bulged adenine. Sequence forms duplex with U2 snRNA positioning adenine for chemistry. Mutations in this motif cause exon skipping, inherited disease such as thalassemia, emphasizing sequence conservation importance.