Final answer:
People who are homozygous for the sickle cell gene have sickle cell disease. This condition is caused by inheriting two copies of the mutated gene, one from each parent, which leads to the production of abnormal hemoglobin and sickled red blood cells.
Step-by-step explanation:
The question is asking whether having homozygous genes for the sickle cell trait results in sickle cell disease. The correct answer is true. Sickle cell disease is caused by a mutation in the HBB gene that codes for hemoglobin. Individuals with sickle cell disease have inherited two copies of the sickle cell gene (one from each parent), making them homozygous for the mutation. Being homozygous for the sickle cell allele means that a person will exhibit the symptoms of sickle cell disease, as their red blood cells will assume a sickled shape under low oxygen conditions, which can lead to various health complications. Those who are heterozygous (carrying one normal allele and one sickle cell allele) usually do not show symptoms of the disease and are often referred to as carriers.