A report of a newly identified syndrome in families of the Old Order Amish showed that the lethal condition that resulted from numerous, multisystem abnormalities is inherited as an autosomal recessive. SNP-based mapping showed that a portion of a region on chromosome 6p, namely the ICK gene (intestinal cell kinase), was homozygous in all autopsied patients but heterozygous in normal members of the affected families. The mutation seems so far to be specific only to the Amish. Which of the following would be a reasonable next step in studying this mutation?

A) sequencing to identify the abnormality in the ICK gene

B) use of a microarray to see whether the gene is expressed in heterozygotes

C) kinase activity assays in adult affected members of the families

D) development of a gene-based test for assessing carrier risk

E) development of a gene-based test for prenatal diagnosis

please explain, so I can assess validity