If there was a chain of seven amino acids, how many possibilities are there for different proteins?

The diversity of proteins is caused by the mRNA codons and DNA. 
DNA has sequences that mRNA finds the pair for (ex. DNA says AGC, RNA says UCG) 
with that, they only come in 3 nucleotide increments. which is a codon 
one you have a codon, it goes thru tRNA to come out with an amino acid and a bunch of amino acids makes a polypeptide or protein 
It all depends on what the DNA's code says to make... 
DNA says AUG, RNA makes that UAC which is the amino acid tyrosine 
did I help?

so basically 7