The GenBank format is widely used to represent annotated nucleotidic sequences.
It contains several keys and subkeys to describe sequence characteristic.
Each sequence starts by the key LOCUS and terminates by //. The record
can contain more than one sequence. 

Example: 

LOCUS       HUMALB1                 1286 bp    DNA     linear   PRI 13-JUL-2001
DEFINITION  Human albumin gene, exon 1 and 5' flank.
ACCESSION   M13075
VERSION     M13075.1  GI:178330
KEYWORDS    albumin; serum protein.
SEGMENT     1 of 2
SOURCE      Homo sapiens (human)
  ORGANISM  Homo sapiens
            Eukaryota; Metazoa; Chordata; Craniata; Vertebrata; Euteleostomi;
            Mammalia; Eutheria; Euarchontoglires; Primates; Catarrhini;
            Hominidae; Homo.
ORIGIN      
        1 gaggtagaga taagaacctt gggtagggaa ggaagattta tgaaatattt aaaaaattat
       61 tcttccttcg ctttgttttt agacataatg ttaaatttat tttgaaattt aaagcaacat
       ...
//