Noun
branchpoint (plural branchpoints)
The point at which a branch occurs
First, the 2'OH of a specific branchpoint nucleotide within the intron, defined during spliceosome assembly, performs a nucleophilic attack on the first nucleotide of the intron at the 5' splice site, forming the lariat intermediate. Source: Internet
Further upstream from the polypyrimidine tract is the branchpoint, which includes an adenine nucleotide involved in lariat formation. Source: Internet