Final answer:
Polycythemia vera is a blood disorder characterized by a mutation in the JAK2 gene, leading to excessive production of red blood cells and increased blood viscosity.
Step-by-step explanation:
Polycythemia vera is a blood disorder that occurs due to a mutation affecting the hemopoietic growth factor pathway. Specifically, it is typically associated with a mutation in the JAK2 (Janus kinase 2) gene.
This mutation leads to the uncontrolled production of blood cells, mainly red blood cells (RBCs), by the bone marrow. This condition results in an elevated level of hemoglobin and, consequently, an increased blood viscosity, which makes it harder for the heart to pump blood.
It is important to understand the distinction between normal physiological responses that cause elevated RBC counts, such as adaptation to high altitude, and polycythemia vera, which is a pathological condition.