A man with the autosomal recessive disorder phenylketonuria (PKU) and a woman without PKu heve a son named Peter, who does not have PKU. Peter is curious about whether hs mother is a carrier for PKiu Which fact would allow him to know Peter's matemal grandmother does not have PkU.
1. Peter's maternal grandfather does not have PkU
2. Peters maternal grandfather has PKu
3. Peter submits his own blood semple to a local genotyping lab, which establishes that he is a carrier for Pku
4. Peter's own daughter has PKU