Synthetic antisense oligomers (illustrated below) that are used to functionally inactivate specific genes. The genetic bases adenine (A), cytosine (C), guanine (G), and thymine (T) are each attached to morpholine rings, and these are linked in a specific order by non-ionic phosphorodiamidate moieties. In spite of its altered backbone, a Morpholino still binds by Watson-Crick base-pairing to sequences of polynucleotides that have complementary base sequences. Since Morpholinos are not negatively charged, they are less likely to interact non-selectively with charged proteins found within cells. Morpholino-RNA hybrids are not substrates for ribonuclease H (q.v.), and Morpholino oligomers are not attacked by various nucleases commonly found in cells. Because of these properties, Morpholinos are routinely used for generating mutant phenotypes. See Chronology, 1997, Summerton and Weller; antisense RNA (asRNA), double-stranded RNA (dsRNA), morphants, RNA interference (RNAi).
Morpholinos Illustration by Jon D. Moulton, Gene Tools, LLC, Philomath, OR. Reproduced with his permission.
Subjects: Genetics and Genomics.