Deletion of one 'T' residue from a string of 5 'T' residues.
Mutation in sequenced strain: frameshift (-1) (see FBrf0168007).
There is a -1 frameshift in Gr22d in iso-1, the reference sequence strain relative to Oregon-R. A string of 4 Ts in iso-1 corresponds to 5 Ts in Oregon-R.
Dunipace et al. (FBrf0137203) concluded that Gr22d was a pseudogene on the basis of this mutation. However Robertson (FBrf0168007) shows this to be a strain specific mutation.