Amino acids are subunits of bases, sugars, and phosphates that make up parts of a DNA sequence.  While the sugar and phosphate parts are identical for each amino acid, the base is what makes the amino acid different.  There are four bases: adenine, thymine, guanine, and cytosine.  The bases pair with each other like this : adenine bonds with thymine (A-T), while guanine bonds with cytosine (G-C).  These bases are often in three-base units, called a codon.  If you are doing a project, or answering a question that calls for the construction of an amino acid sequence, it is as simple as using these four bases in three-base groups, strung together as one, like this:

ATAGCGTTTATA

I saw you listed mutations in your comments area.  There are three common mutations in genetic code, insertion, deletion, and substitution.  Insertion is when you insert another base into the original code, like this:

ATACGCGTTTATA

Deletion is when you do the exact opposite, pull a base out of the original code, like this:

ATGCGTTTATA

Substitution is when you pull a base from the original code and substitute it with one of the other three bases, like this:

ATAGCGTCTATA