Question

Sickle cell anemia is caused when an amino acid substitution in one of the polypeptide chains that makes hemoglobin occurs. Consequently, the hemoglobin structure is sickle-shaped instead of sphere-shaped. Which of the following is the sequence of events described above?

1) Transcription, translation, amino acid substitution
2) DNA replication, transcription, translation
3) DNA replication, amino acid substitution, translation
4) Transcription, DNA replication, translation

Answer 1

Sickle cell anemia involves a single amino acid substitution in the hemoglobin protein, and the correct sequence leading to this condition is transcription, and translation, followed by amino acid substitution.

Step-by-step explanation:

Sickle cell anemia is caused by a single amino acid substitution in the hemoglobin β-chain, where valine replaces glutamic acid. This substitution is a result of a point mutation in the DNA that alters the mRNA and the protein product during translation. The correct sequence of events leading to sickle cell anemia is: first, the gene is transcribed to produce mRNA, then, during translation, due to the mutation, an incorrect amino acid (valine) is incorporated instead of the normal one (glutamic acid), leading to the abnormal structure of the hemoglobin.

Hemoglobin is vital for oxygen transport, and the distorted shape of sickle cells impedes normal blood flow and oxygen delivery, leading to the symptoms of sickle cell anemia. The correct sequence of events is thus: Transcription, translation, and amino acid substitution, as it captures the flow from gene to protein alteration that characterizes the condition.