Biochemistry 7-methyl guanosine is added as a cap on mRNA. This methyl group is donated by: A S-Adenosyl methionine (SAM) B Methenyl THF C Tetra hydro Folate (THF) D Vit B12 💡 Explanation 7-methyl guanosine is added as a cap on mRNA. This methyl group is donated by: ✓ Correct Answer: A. S-Adenosyl methionine (SAM)