Final answer:
Sickle cell anemia is caused by a point mutation that leads to a missense mutation, replacing glutamic acid with valine in hemoglobin. This causes red blood cells to sickle, obstructing blood flow and causing anemia. Heterozygous individuals have the sickle cell trait with less severe symptoms and some resistance to malaria.
Step-by-step explanation:
How Point Mutation Leads to Sickle Cell Trait:
A point mutation in the DNA sequence can have significant effects on protein function. In the case of sickle cell anemia, a single nucleotide change from A to T at the 17th nucleotide of a hemoglobin gene results in a missense mutation. This substitution changes the amino acid from glutamic acid (GAG) to valine (GTG). Because amino acids determine the shape and function of a protein, this change leads to the production of abnormal hemoglobin, which makes red blood cells sickle or crescent-shaped. Heterozygous individuals who possess one mutated gene and one normal gene have the sickle cell trait, generally leading to a less severe condition than those who carry two copies of the mutation (homozygous), which results in full-blown sickle cell anemia. Heterozygotes often exhibit resistance to malaria, which supports the hypothesis of protection in certain regions where the disease is prevalent.
Impact of Sickle Cell Gene Mutation
The abnormal hemoglobin caused by this point mutation can lead to serious health issues. Sickled cells disrupt normal blood flow and oxygen delivery, causing the symptoms associated with anemia. These cells can clog blood vessels leading to pain, swelling, and potential tissue damage. The sickle cell gene affects millions worldwide and has a high prevalence in African-American populations due to its protective effect against malaria.