Before she received gene therapy treatment, Jennelle suffered bone and joint pain from sickle cell disease. Like sickle cell, thalassemia is a blood disease caused by a mutation in one gene. In the case of thalassemia, the mutated gene is the one that codes for alpha globin, resulting in a lack of (or reduction in) alpha globin production. When two parents are heterozygous for thalassemia, they are unaffected. Among their children, there is a 25 percent chance that a child will be homozygous for thalassemia and will express thalassemia as a major trait, a 25 percent chance that a child will not carry the gene for thalassemia, and a 50 percent chance that the child will be heterozygous, and an unaffected carrier like the parents. Which of the following describes thalassemia?

Question

Before she received gene therapy treatment, Jennelle suffered bone and joint pain from sickle cell disease. Like sickle cell, thalassemia is a blood disease caused by a mutation in one gene. In the case of thalassemia, the mutated gene is the one that codes for alpha globin, resulting in a lack of (or reduction in) alpha globin production. When two parents are heterozygous for thalassemia, they are unaffected. Among their children, there is a 25 percent chance that a child will be homozygous for thalassemia and will express thalassemia as a major trait, a 25 percent chance that a child will not carry the gene for thalassemia, and a 50 percent chance that the child will be heterozygous, and an unaffected carrier like the parents. Which of the following describes thalassemia?

A. recessive
B. homozygous
C. dominant
D. sex-linked
E. heterozygous

Answer 1

A. recessive

Thalassemia is a recessive genetic disorder, meaning that both copies of the gene must be mutated in order for the disease to be expressed. In the case described, individuals who are heterozygous for thalassemia are unaffected carriers of the gene. Only individuals who are homozygous for thalassemia will express the disease as a major trait.