first noticed in newborns when the urine in their diapers turnsblack upon exposure to air. The condition is caused by thedefective transport of the amino acid phenylalanine through theintestinal walls during digestion. About 4 people per 1000 arecarriers of alkaptonuria.
Sara and James had never heard of alkaptonuria and were shocked todiscover that their first child had the condition. Sara's sisterMary and her husband Frank are planning to have a family and areconcerned about the possibility of alkaptonuria in one of theirchildren.
The four adults (Sara, James, Mary, and Frank) seek informationfrom a neighbor who is a retired physician.
After discussing their family histories, the neighbor says, "I never took genetics, but I knowfrom my many years in practice that Sara and James are bothcarriers of this recessive condition. Since their first child hadthe condition, there is a very low chance that the next child willalso have it, because the odds of having two children with arecessive condition are very low. Mary and Frank have no chance ofhaving a child with alkaptonuria because Frank has no familyhistory of the condition."
The two couples each have babies and both babies havealkaptonuria.
Part A
The neighbor was apparently incorrect in her assessment thatthere would be "no chance" of Mary and Frank having a child withalkaptonuria. Assume that before the birth of Mary andFrank's baby, you had been asked...
What would the probability be of Mary and Frank having a childwith alkaptonuria?
Enter your answer as a reduced fraction. For example: 1/2, not8/16 or 0.50
Part B
What is the chance that the third child of Sara and James willbe free of the condition?
Enter your answer as a reduced fraction. For example: 1/2, not8/16 or 0.50
Part C
Sara and James are now worried that one of theirgrandchildren will inherit alkaptonuria. What is thechance that the first child of their daughter with alkaptonuriawill be affected by alkaptonuria? Assume that their son-in-law hasno family history of alkaptonuria.
Enter your answer as a reduced fraction. For example: 1/2, not8/16 or 0.50.