Which mRNA base must be the one which is substituted in the sixth codon that would result in the change of GLU (glutamic acid), whose mRNA codon is GAG into Val

The mRNA base that must be substituted is A. A is substituted by U.

Explanation: In the sixth position of the beta chain of hemoglobin, valine replaces glutamine acid. The effect of this substitution is an abnormal red blood cells with a sickle shape. Every amino acid is coded for by a least one codon. A codon is a triplet of nucleotides in a mRNA. The mRNA codons for glutamic acid are GAA and GAG, while the mRNA codons for valine are GUU, GUC, GUA and GUG.

When the base Adenine (A) in the mRNA codon GAG which codes for glutamic acid is substituted by the base Uracil (U), the new mRNA codon will be GUG which codes for valine.

the national environmental policy act (nepa) is a united states environmental law that promotes the enhancement of the environment and established the president's council on environmental quality (ceq). the law was enacted on january 1, 1970. to date, more than 100 nations around the world have enacted national environmental policies modeled after nepa.