  The KE family has received much press since the early 1990s, when  Gopnik 1990a,b and Gopnik and Crago 1991 (see also Gopnik 1997)  proposed that their morphosyntactic deficits were caused by a  mutation in a single dominant gene normally responsible for the  encoding of grammatical features, such as function words and the  inflections used to mark number, tense, aspect, etc. According to  Gopnik, the affected KE's are ‘feature blind’ as a  consequence of this mutation. And according to Pinker (1994), their  pedigree (Fig. 6) and specifically morphosyntactic deficits  constitutes “suggestive evidence for grammar genes …  genes whose effects seem most specific to the development of the  circuits underlying parts of grammar” (Pinker 1994:325).