Case Study: Cell Biology And Genetics

Marsha and Clement are both carriers of sickle cell disease, a disease that is autosomal recessive. Their first child, Amelia, does not have the disease. Marsha and Clement are planning another pregnancy, but they are concerned about their second child having the condition. Clement’s dad died from complications of sickle cell disease shortly before Amelia was born.

1. Draw a Punnett square to determine the likelihood of Marsha and Clement having a baby with sickle cell disease. What is the chance the baby will be a carrier of the disease, just like the parents?

2. Marsha suggested to the nurse at the local family planning clinic that if the baby were a boy he might have a higher risk for developing the disease, just like his grandfather. If you were this Practitioner, how would you respond?

3. When Amelia, who does not have sickle cell disease, grows up and marries someone who does have the disease, how likely is it that her children will have the disease?

Maria is a sedentary, 68-year-old woman who is overweight. She complains that her hands and feet are always cold, and she tires quickly when cleaning the house. At her most recent visit to her doctor, her blood pressure was 184/98 mm Hg. She has edema around her ankles and legs, and her physician is concerned about an echocardiogram that indicates Maria has an enlarged heart.

1. Identify two reasons why Maria will have tissue ischemia. How might this lead to hypoxia?

2. What two early and reversible changes occur to tissue cells when they are hypoxic?

3. What specific type of cellular adaptation has taken place in Maria’s enlarged heart? What made you come to this conclusion?

4. Predict why Maria’s heart has become enlarged. Why doesn’t this enlargement give her the same cardiac strength and endurance as a well-trained athlete?

Kevin worked for 10 years at a uranium mine, excavating uranium for a nearby nuclear power plant. Now, 25 years later, he has small cell lung cancer. Kevin is anorexic and has lost a considerable amount of weight. His muscles are wasting, and he is weak. He tries to move around the house throughout the day but tires easily. It has been difficult for him to access care, and the treatment for his cancer is just starting.

1. With the ongoing exposure to the ionizing radiation, DNA damage occurred. Outline the three stages of carcinogenesis that occurred after his exposure to radiation.

2. Kevin is normally a fit and active man, and his wife often commented on how much food he used to eat after a day at mine. Why would there be muscle wasting and weight loss now? Explain your answer using your

3. knowledge of the metabolic changes seen with cancer.

4. In some cancer patients, muscle weakness may result from the production of onconeural antigens. Describe the effects of these antigens. What form would this process likely take in Kevin’s situation?

Felicity is a very busy 29-year-old woman in a professional career. She has diabetes mellitus, and is also pregnant for the first time. Due to her busy schedule, it took her three weeks to visit the family doctor to have the pregnancy confirmed. Felicity became very concerned when her physician asked whether she had been taking folic acid. It was all Felicity could do to remember to manage her insulin levels, and taking folic acid supplements was something she hadn’t even considered. Her doctor told her to take 600 μg of folic acid daily and advised Felicity to return later for maternal serum marker testing.

1. Explain the potential teratogenic effect of folic acid deficiency on the developing fetus. What other risk factor is noteworthy in Felicity’s case?

2. What is the benefit of maternal serum marker testing? What other test would be particularly useful to monitor the development of Felicity’s baby in this situation?

3. When is the fetus most vulnerable to the effects of teratogens and why?