What is point mutation? Give one example.
Point mutation is a type of mutation that occurs due to a change in a single base pair of DNA. This alteration in the genetic material can lead to changes in both the genotype and phenotype of an organism.
A classic example of point mutation is sickle cell anemia. This genetic disorder is caused by a change of one base in the gene coding for the beta-chain of hemoglobin. Specifically, there is a single base substitution at the sixth codon of the beta globin gene from GAG to GUG, which results in the substitution of glutamic acid by valine at the sixth position of the beta globin chain. This leads to the formation of abnormal hemoglobin that causes red blood cells to assume a sickle shape.
Explanation
The answer correctly defines point mutation as a change in a single base pair of DNA, as stated in the textbook. It also provides sickle cell anemia as the required example, which is explicitly mentioned in the context as a classic example of point mutation. The explanation includes specific details about how the mutation causes the disease (GAG to GUG substitution leading to glutamic acid being replaced by valine), demonstrating a comprehensive understanding of the concept.
Solution Steps
Step 1: Define point mutation based on the textbook definition - a change in a single base pair of DNA.
Step 2: Identify an example from the context - sickle cell anemia.
Step 3: Explain how sickle cell anemia is caused by point mutation (single base substitution from GAG to GUG in the beta globin gene).