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You are a second-year medical student in an innovative medical school that allow

ID: 99431 • Letter: Y

Question

You are a second-year medical student in an innovative medical school that allows you to get in-depth clinical

experience early in your medical education. You are currently assigned to work with Dr. Aikenhed, a pediatric

oncologist. She has done a biopsy on a tumor-like growth in the adrenal gland of her 17-year-old patient, Lee F. You

write down the following notes while Dr. Aikenhed takes a detailed family history from the patient’s parents:

• Lee has a sister, Leah (age 10), and a brother, Luke (age 6). Both are healthy.

• Lee’s mother, Grace, was diagnosed with bilateral breast cancer last year at age 35. Lee’s father, Brian, and Lee’s paternal grandparents have no history of cancer.

• Grace is the youngest of four children. Her eldest brother, Greg (age 42), and sister, Greta (age 40), have never had any signs or symptoms of cancer. She had a brother, Geoff, who died of leukemia at age 8. He was the third child of Grace’s parents.

• Greg’s two fraternal twin daughters have no signs or symptoms of cancer.

• Grace’s father, Roger, died of a soft tissue sarcoma at age 35. Grace’s mother, Renee, is still living and in excellent health.

• Roger’s mother died of a brain tumor at age 30. Roger was her only child1-Complete the following table to help organize your thoughts. Indicate in the table if a mode of inheritance is definitely possible, possible but unlikely, or not possible based on the pedigree. Also briefly explain your rationale behind these choices in the space provided.

Mode of Inheritance

possible

Possible but unlikely

Not possible

Brief rational

Autosomal recessive

Autosomal dominant

X-linked recessive

X-linked dominant

Y-linked

Mitochondrial

2. What mode of inheritance pattern best fits this pedigree in your opinion?

Mode of Inheritance

possible

Possible but unlikely

Not possible

Brief rational

Autosomal recessive

Autosomal dominant

X-linked recessive

X-linked dominant

Y-linked

Mitochondrial

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Explanation / Answer

Mode of Inheritance

possible

Possible but unlikely

Not possible

Brief rational

Autosomal recessive

Not Possible

There can be carrier of disease but each generation is not affected by disease.

Autosomal dominant

Possible

In this case inheritance takes place from affected parent and the chances are 50%. it is independent of sex.

X-linked recessive

Not possible

There is no male to male transmission in this case.

X-linked dominant

Not possible

There is no male to male transmission in this case.

Y-linked

Not possible

Inheritance is from father to son only.

Mitochondrial

Not possible

Inherited by mothers only.

2. Autosomal dominant inheritance best fits the case as every genration shows inheritance of disease. All affected individuals have atleast one parent affected with disease. This is seen in the given case.

Mode of Inheritance

possible

Possible but unlikely

Not possible

Brief rational

Autosomal recessive

Not Possible

There can be carrier of disease but each generation is not affected by disease.

Autosomal dominant

Possible

In this case inheritance takes place from affected parent and the chances are 50%. it is independent of sex.

X-linked recessive

Not possible

There is no male to male transmission in this case.

X-linked dominant

Not possible

There is no male to male transmission in this case.

Y-linked

Not possible

Inheritance is from father to son only.

Mitochondrial

Not possible

Inherited by mothers only.