Which of the following statements about sickle cell disease is TRUE?It causes a person’s mucus to the excessively thick and sticky.It primarily affects people of African descent.It is caused by having 3 copies of chromosome 21.It is a mild, painless illness that does not limit lifespan.

Sure, let's analyze each statement step by step to determine which one is true about sickle cell disease:

1. "It causes a person’s mucus to be excessively thick and sticky."

   • This statement is false. This description is characteristic of cystic fibrosis, not sickle cell disease.

2. "It primarily affects people of African descent."

   • This statement is true. Sickle cell disease is more common among people of African descent, although it can also affect people from other ethnic backgrounds, including those of Mediterranean, Middle Eastern, and Indian descent.

3. "It is caused by having 3 copies of chromosome 21."

   • This statement is false. Having 3 copies of chromosome 21 causes Down syndrome, not sickle cell disease. Sickle cell disease is caused by a mutation in the HBB gene on chromosome 11.

4. "It is a mild, painless illness that does not limit lifespan."

   • This statement is false. Sickle cell disease can cause severe pain, complications, and can significantly impact a person's quality of life and lifespan.

Therefore, the true statement about sickle cell disease is:

"It primarily affects people of African descent."