Question

Using the genetic code shown here, predict what type of mutation has occurred in the hemoglobin sickle-cell anemia allele.

O normal allele 5'–ggaaugaaacaggaaccc–3'
O mutant allele 5'–ggaaugaaacagguaccc–3'

Answer 1

The mutation causing sickle cell anemia in hemoglobin is a missense mutation, where a single nucleotide change alters a codon, substituting valine for glutamic acid at position seven of the beta chain, altering the protein's structure and function.

Step-by-step explanation:

The mutation in hemoglobin that leads to sickle cell anemia is a missense mutation. In this genetic disorder, a single base change converts a codon for the amino acid glutamic acid (GAG) to a codon for valine (GTG). This alteration occurs on the gene encoding the beta chain of hemoglobin, specifically at the seventh amino acid position.

In the sequence provided, the normal allele is 5'–ggaaugaaacaggaaccc–3', where the codon GAG codes for glutamic acid. In the mutant allele, the sequence is 5'–ggaaugaaacagguaccc–3', indicating a single nucleotide change from 'GAG' to 'GTG'. This results in the substitution of valine for glutamic acid, leading to the sickle cell trait.

Sickle cell anemia is noted for the profound effect a single amino acid exchange can have on the overall function and shape of hemoglobin, exemplified by sickle-shaped red blood cells. With approximately 600 amino acids in a hemoglobin molecule, encoded by three nucleotides each, the disease underscores the importance of precision in the genetic code where a single point mutation can have significant biological consequences.