Question

Mutations

1. Explain how a mutation in one of the hemoglobin subunit genes leads to symptoms of low blood oxygen, fatigue, and clogged capillaries. In your explanation, include the effect of the mutation on the primary, tertiary, and quaternary levels of protein synthesis and connect the protein’s attributes to the sickle-shaped red blood cells. In your explanation, compare the mutant subunit to the normal subunit.

Answer 1

Sickle cell anemia is an autosomal recessive disorder of the hematopoietic system, in which the red blood cells become sickle-shaped and cannot carry oxygen. The symptoms include the decreased hemoglobin, high reticulocyte count, and bilirubin levels. The high bilirubin is due to the damage of abnormal RBC.

Codominance expressed by heterozygous alleles in which one is normal and another is a mutant form that coexists, thereby the heterozygous for sickle cell allele results in both normal and abnormal hemoglobin in the circulating blood. This codominance associated with the increased prevalence of sickle cell disease among African Americans actually has more to do with the environment than skin color or other phenotypes used to define races.

Point mutation - result in sickle cell anemia (11th chromosomal co-dominance effect)

The 147th position of the beta chain of the hemoglobin- 6th glutamic acid replaced by valine (E6V). Since glutamic acid is a negatively charged amino acid and valine is neutral, the mutated HbS contains the slight negative charge. The altered primary protein structure (amino acid sequence) of the protein also alter the secondary and tertiary protein structure, which results in the formation of sickle-shaped cells.

Codominance expressed by heterozygous alleles in which one is normal and another is the mutant form that coexists, thereby the heterozygous for sickle cell allele result in both normal and abnormal hemoglobin in the circulating blood. The heterozygotes remain normal similar to the people with wild-type alleles and they do not exhibit the severe symptoms of sickle cell disease.