Pedigree Analysis: Galactosemia
Galactosemia is a human genetic disorder caused by a deficiency of the enzyme galactose-1-phosphate uridylyltransferase (commonly called GALT).
Children with galactosemia seem normal at birth, but begin to show symptoms as soon as they drink milk. This is because they cannot metabolize galactose, a simple sugar that results from the breakdown of lactose (the sugar found in milk).
Early symptoms of galactosemia include vomiting and diarrhea. If untreated, affected babies will develop enlarged livers, cataracts, and mental retardation. Depending on the alleles the baby has inherited, early death may result.
Part A - Construct a pedigree
John and Jane Jones’ newborn baby girl, Leah, has just been diagnosed with galactosemia. Prior to their genetic counseling appointment, they submitted this family history:
John and Jane’s older child, a son named Lee, does not have galactosemia.
John is the only child of Hanna and Harry.
Harry was an only child. Hanna has two older sisters, Hope (the oldest) and Holly.
Both Harry and Hanna’s parents lived in good health into their 80s.
Jane’s brother, Joe, is married to Jen. They have a son, Les, who is a healthy nine-year-old with myopia (nearsightedness) but no sign of galactosemia.
Jane’s mother, Hilda, is alive and healthy; Jane’s father, Henry, passed away last year of a sudden heart attack. Hilda and Henry have no family history of galactosemia.
Use the information in the family history to construct a pedigree for this family.
Drag the correct symbols to their appropriate locations on the pedigree below. Not all symbols will be used. See the Hints for help getting started.