Seafood -- including clams, trout, salmon, sardines, haddock and oysters -- are a rich source of B12. Clam mollusks contain 84.1 micrograms and oysters contain 13.3 micrograms per 3 ounces. Vitamin B12 is also found in cod, catfish, crab and swordfish. Consume milk, cheese and yogurt to increase your daily B12 intake.eady-to-eat breakfast cereals are an excellent source of B12 and folic acid. Folic acid is also added to rice, egg noodles, bread, pasta, corn meals, orange drinks and tomato juice. Tomato juice provides 10 percent of the daily value per 6 ounces and egg noodles provide 15 percent of folic acid in 1/2 cup.
If it was one DNA letter for one amino acid then you could only code for a maximum of four amino acids. Two letters in every possible combination could code for up to sixteen amino acids. Still, not enough. But three DNA letters provide more than enough combinations to code for all twenty amino acids.
And what about proteins that have exact similar properties but different amino acids combinations. For instance, let's take hemoglobin. It generally has 146 amino acids, but not all them are essential for the protein to be functional. So, if we a ask a question as to how many different amino acids are necessary for the protein to be known as the  hemoglobin  protein, then the answer depends on many things. Whenever changes in amino acid affects the physical structure of protein molecule, the affected protein becomes inactive.