Reference no: EM133889305

Jennie and Stewart Smith were so excited at the birth of their baby Jared. Both the pregnancy and delivery had been uneventful. But in the back of their minds, they really were worried because their first child, Sarah, died at the age of nine days. By the fifth day after birth, Jared began to have trouble nursing and by the seventh day he had completely stopped feeding. Jennie and Stewart rushed Jared to the emergency room. Although his limbs were rigid and he had had a seizure, the examination showed no infection and his x-rays were normal. The doctor also did routine lab tests on his blood and urine. "Doctor, do you think that this funny smell in Jared's diapers has anything to do with his problem?" Jennie asked. "I brought one along so that you could smell it too." The urine did have a peculiar order of boiled cabbage and lab results revealed elevated levels of tyrosine metabolites and succinylacetone.

Skin biopsies from the baby and his parents were taken and cultured for the ability to metabolize the amino acid tyrosine. While the parents' enzyme activity levels were nearly normal, Jared's was less than 1% of normal. Given this information, Jared was diagnosed with Tyrosinemia Type 1 and will not be able to breast feed or consume regular formula and a low protein diet is needed for the rest of his life.

Jennie and Stewart are Old Order Amish and their family history revealed that Jennie's mother had two sisters who died in their first year of life; no one knew why. Stewart's father had a sister who died at seven months of age from unknown cases. Could the gene for Tyrosinemia Type 1 run in both of their families?

Questions:

1. What gene is causes Tyrosinemia Type 1 disorder?

2. What is the inheritance pattern for this disease?

3. Define the terms a) genotype, b) phenotype, c) homozygous and d) heterozygous.

4. Draw a pedigree chart to explain the relationships and the disease in this family. Be sure to include Jennie, Stewart, Jared and Sarah. Also include Jennie's father, Jennie's mother, Jennie's aunts, Jennie's grandparents, Stewart's mother, Stewart's father and Stewart's aunt and Stewart's grandparents and indicate who are potential carriers

5. How could their son have inherited TT1 even though neither parent suffers from it?

6. What is the probability that they would have another affected child? A carrier?

7. Could Jennie and Stewart have children who do not have TT1 (i.e. phenotypically normal)? Explain. What is the probability of having a phenotypically normal child - phenotypic not genetic?

8. If TT1 was an x-linked dominant disorder, what would the probability be that Jared would inherit the disease?

9. Why were Jennie and Stewart's enzyme levels nearly normal?