Question

Many different types of mutations can occur within the body. An individual experiences a mutation that changes a base in a mRNA strand, but during translation the mRNA strand still creates the same protein. Which type of mutation is responsible for the change in the mRNA base?

Answer 1

Answer:

Explanation:

Although the haploid human genome consists of 3 billion nucleotides, changes in even a single base pair can result in dramatic physiological malfunctions. For example, sickle-cell anemia is a disease caused by the smallest of genetic changes. Here, the alteration of a single nucleotide in the gene for the beta chain of the hemoglobin protein (the oxygen-carrying protein that makes blood red) is all it takes to turn a normal hemoglobin gene into a sickle-cell hemoglobin gene. This single nucleotide change alters only one amino acid in the protein chain, but the results are devastating.

Beta hemoglobin (beta globin) is a single chain of 147 amino acids. As previously mentioned, in sickle-cell anemia, the gene for beta globin is mutated. The resulting protein still consists of 147 amino acids, but because of the single-base mutation, the sixth amino acid in the chain is valine, rather than glutamic acid. This substitution is depicted in Table 1.

Table 1: Single-Base Mutation Associated with Sickle-Cell Anemia

Sequence for Wild-Type Hemoglobin

ATG GTG CAC CTG ACT CCT GAG GAG AAG TCT GCC GTT ACT

Start Val His Leu Thr Pro Glu Glu Lys Ser Ala Val Thr

Sequence for Mutant (Sickle-Cell) Hemoglobin

ATG GTG CAC CTG ACT CCT GTG GAG AAG TCT GCC GTT ACT

Start Val His Leu Thr Pro Val Glu Lys Ser Ala Val Thr

Molecules of sickle-cell hemoglobin stick to one another, forming rigid rods. These rods cause a person's red blood cells to take on a deformed, sickle-like shape, thus giving the disease its name. The rigid, misshapen blood cells do not carry oxygen well, and they also tend to clog capillaries, causing an affected person's blood supply to be cut off to various tissues, including the brain and the heart. Therefore, when an afflicted individual exerts himself or herself even slightly, he or she often experiences terrible pain, and he or she might even undergo heart attack or stroke—all because of a single nucleotide mutation