Day 3, April 10 2008

Today, we have begun answering the questions. Questions 1-6 discuss pedigree construction and autosomal dominant traits.
1) What would a pedigree of Mr. and Mrs. Smith families look like? Concentrate simply on family relationships and affected persons.

• Their pedigrees would show family members who posess each disease. It will also the predominance of the disease in each gender. Based on the pedigrees of both families and the information the spouses acquire from the doctor about genetic information transmition, they will see it fit or unfit to have children.

2) Do autosomal dominant disorders skip generations?

• No, because every affected individual has an affected biological parent.

3)Could Mr Smith or his mother be carriers of the gene that causes myotonic dystrophy?

• No, because autosomal dominant traits, if possessed, are always manifested.

4)Is there a possibility that Mr Smith's aunt or uncle is homozygous for the myotonic dystrophy (MD) gene?

• No, because the father of Mr Smith's aunt and uncle did not possess the dominant trait so Mr Smith's uncle and aunt are heterozygous. Their mother passed the dominant trait to them.

5)Symptoms of myotonic dystrophy sometimes don’t show up until after age fifty. What is the possibility that Mr Smith's cousin has inherited the MD gene?

• Mr. Smith's cousin has a 50% chance of having inherited the disease because one of her parents is heterozygous for the autosomal dominant trait.

6)What is the possibility that Mr and Mrs Smith's children could inherit the MD gene?

• There is no possibility of the child inheriting the disease because he has no affected parent with myotonic dystrophy. Due to the fact that this is an autosomal dominant disease, if one of the parents had inherited it, they would show symptoms. Only Mr Smith has history of this disease, but neither of his parents (who are older than 50 years old) have it.