Question

The change of a single base in the DNA sequence for normal hemoglobin can encode for the abnormal hemoglobin, giving rise to sickle cell anemia. Which base in the codon for glu in DNA is replaced to give the codon(s) for val?

Short answer

DNA sequences are CAT and CAC.

Step-by-step solution

Sickle cell anemia

Sickle cell anemia is a blood disorder and a hereditary problem. The shape of the red blood cells become a crescent shape, often leading to infections, tiredness, delayed growth, and puberty in children.

Explanation

First, we will write down mRNA codes for glutamic acid and valine amino acids.

mRNA sequences for glutamic acid are GAA and GAG.

mRNA sequences for valine are GUU, GUC, GUA and GUG.

If we replace the second base (A) with U, the translation will result (GUA and GUG) in forming valine instead of glutamic acid.

A DNA sequence is complementary to the mRNA sequence. Therefore, the complementary sequence to GUA is CAT, and the complementary sequence to GUG is CAC

Hence, DNA sequences are CAT and CAC.