Treatment of a human genetic disease may involve an attempt to modify the abnormal phenotype by restricting the substrate of a deficient enzyme, inhibiting a harmful metabolic reaction, or supplying a missing protein. By contrast, gene therapy aims to address a genetic defect by inserting a normal allele into a patient’s cells.
learning outcomes
You should be able to:
Explain how a genetic disease can be treated by modifying the disease phenotype.
Compare ex vivo and in vivo approaches to gene therapy.
How do metabolic inhibitors function in treating genetic diseases such as cancer?
Metabolic inhibitors block important chemical transformations in cancer cells. An inhibitor may either block the accumulation of a harmful substance or block cancer-
How does in vivo gene therapy work? Can you give an example?
In vivo gene therapy inserts the wild-
In the past, it was common for people with phenylketonuria (PKU) who were placed on a low-
Why is the fetus likely to be heterozygous?
What do you think would happen to the fetus during this “maternal PKU” situation?
What would be your advice to a woman with PKU who wants to have a child?
The mutation that leads to PKU is rare in the human population; most people do not have the harmful allele, and the highest probability is that the father is homozygous normal. Because the mother has PKU (she is homozygous mutant), the developing fetus is heterozygous.
High levels of phenylalanine cause brain damage. If the mother’s phenylalanine levels were too high, the baby would be born with brain problems.
The woman should be on a phenylalanine-
In this chapter you have learned about mutations, focusing on DNA changes that affect phenotypes through specific protein products. But there is much more to molecular genetics than the sequences of genes and proteins. Determining which genes will be expressed when and where is a major function of the genome. In Chapter 16 we will turn to gene regulation.