If you have whole genome sequencing data from a child and one parent (duo testing), and no information for the other parent, can you look at the reads from whole genome data and determine whether the variant that is not present in the tested parent is de novo in the child versus inherited from the other parent that was not tested? Is there a way to look at nearby or cis variants and determine this or is it absolutely necessary to have trio sequencing to determine if a variant is de novo in the child?