The junction between an exon and an intron at the 5′ end of the intron. When the intron is removed during processing of hnRNA the donor junction is spliced to the acceptor junction at the 3′ end of the exon. Mutations in the invariant GU start or AG termination of an intron have serious consequences for RNA processing; e.g. a patient with a severe form of haemophilia B was shown to have a point mutation in a donor splice junction of the factor IX gene.
Subjects: Medicine and Health.