Question

Sickle cell anemia is a disease that causes difficulty breathing, circulatory problems, and can lead to death. This disease causes red blood cells to be misshapen, so they are sickle-shaped and ridged rather than round, plump, and highly elastic. Sickled cells die more rapidly than healthy cells and therefore lead to reduced oxygen to the tissues and the blockage of blood vessels. Below is the sequence of DNA of a healthy individual and the sequence of DNA that leads to sickle cell anemia.

Normal:... CTG ACT CCT GAG GAG AAG TCT ...
Mutant:... CTG ACT CCT GTG GAG AAG TCT ...
1. Using Table 3.14, characterize the amino acids that have been substituted in the normal and mutant proteins, glutamic acid to valine.
2. Which of the following statements below is TRUE?

Answer 1

Sickle cell anemia is a genetic disorder characterized by the production of abnormal hemoglobin S, caused by a mutation that changes glutamic acid to valine in the hemoglobin gene. This leads to misshapen red blood cells that can obstruct blood flow and decrease oxygen delivery, resulting in serious health issues.

Step-by-step explanation:

Sickle cell anemia is a genetic disorder caused by a mutation in one of the hemoglobin genes. This mutation changes a single amino acid, from glutamic acid to valine, within the hemoglobin protein, leading to the production of an abnormal form of hemoglobin, known as hemoglobin S (HbS). The sequence of DNA that causes sickle cell anemia is shown where the normal sequence 'GAG' codon (glutamic acid) is replaced by a 'GTG' codon (valine) in the mutant sequence.

The substitution of glutamic acid to valine has significant consequences for the affected individual. Glutamic acid is hydrophilic and contributes to the normal, disc-shaped structure of red blood cells, allowing them to remain flexible and efficiently deliver oxygen throughout the body. Valine, on the other hand, is hydrophobic and its presence in hemoglobin causes the red blood cells to assume a sickle or crescent shape. These sickled cells can become lodged in narrow capillaries, leading to various health problems including pain, organ damage, and increased risk of infection.

Abnormal hemoglobin S causes erythrocytes to sickle, leading to reduced oxygen delivery and blockage of blood vessels. This results in difficulties including breathlessness, dizziness, headaches, and abdominal pain for those who have sickle cell anemia. It is a particularly common genetic condition among individuals of African descent, and can have protective effects against malaria when an individual is heterozygous for the mutation.