The code I need to write has the user input a mRna strand which is stored in a char array. This mRNa strand must start with the characters 'a','u','g'. I can't figure out how to validate whether that is true. I thought about getting the sum of the integer values and testing that but I cannot do that because it matches the letters of another 3 letters that can be entered.

also, each three letters translates to an amino acid. I dont know how to take each three letters and translate it. 

An example for my second question
The mRNA string is 
auguuuauu

aug codes for methionine.

uuu codes for phenylalaine.

auu codes for isoleucine.

so the program would go down the line reading each group of 3 and translating it. the values would then be stored in a character array. The way I'm thinking of doing this is making a loop that would store 3 values at a time into a char array. I dont know how to take that char array analyze what that value is and change it to what it needs to be. Once its changed i would just strcat it to the end.