solve the CHAPTER MYSTERY

IN THE BLOOD

Both John and Lila have a genetic disease called familial hyper-cholesterolemia, which is caused by a gene defect on chromosome 19. John is heterozygous for the disorder. Although his liver cells make a mixture of normal and defective LDL receptors, his blood cholesterol levels were so high that he had serious atherosclerosis by age 35. Most people with this disease have had a heart attack by age 60.

Lila is homozygous for the defective allele—a very rare condition. Her liver cells do not produce any functional LDL receptors. Her atherosclerosis became apparent when she was only 4 years old. Fatty deposits can be seen in the corneas of her eyes and beneath the skin near her elbows and knees.

Research on this genetic defect helped uncover the role of liver cell LDL receptors in regulating blood cholesterol. Researchers then applied that information to cases of high cholesterol among the general public. The result was the development of several new classes of drugs that are helping some people live longer.

1. Predict If Lila were to have a child, what is the likelihood that she would pass on the allele for familial hypercholesterolemia to her child? If John had a son, what is the likelihood that the son inherited the allele?

2. Infer Most heterozygous patients can keep their LDL levels under control with medication that prevents their liver from making cholesterol. But these medications generally do not lower the LDL levels of homozygous patients. Why do you think that is so?

3. Connect to the If an individual knows that hypercholesterolemia runs in his or her family, what steps can he or she take to live a long and healthy life?