Question

In normal people roughly 1-2% of the hemoglobin in the blood is spontaneously converted to methemoglobin, in which the iron in the heme group is in the Fe3+ (ferric) state, not the Fe2+ (ferrous) state of normal hemoglobin. Methemoglobin cannot bind oxygen and, unlike oxyhemoglobin, it is bluish-brown in color. The NADH-dependent Cytochrome b5 reductases (CYB5A and CYB5R3) (aka. methemoglobin reductases) are responsible for converting methemoglobin back to hemoglobin and so there are two types of this disease, loss-of-function mutations in CYB5A (type I on chromosome 18) and CYB5R3 (Type II on chromosome 22).

1a) If a blue woman with a CYB5A mutation meets a blue man with a CYB5A mutation while waiting at the doctor’s office and they eventually marry, what genotypes could be produced in their children and in what proportions? Be sure to define any symbols that you use.

1b) If one of their children married another blue person with a CYB5R3 mutation, what are the chances that the offspring of that union would be affected?

1c) If one of the chilren from (1b) married a non-blue person whose parents were both blue, what are the chances that offsprings of that union would be afftected

Answer 1