Biological sequences in FASTA format consist of one line of comments beginning with a '>' symbol (description line), followed by any number of lines of sequence information. Lines except the last are often limited to 80 characters. 

Sequences are expected to be represented in the standard amino acid or nucleic acid codes; N may be used for an unknown nucleic acid residue and X for an unknown amino acid residue. 

It is a multi-sequence file format. Each additional sequence begins on a new line and starts with a single description line. 

Example: 

>this is a dna example 
aaattggccc 
>this is a protein example 
ANGXXXTC