The sequence of nucleotides in a chromosome (DNA, RNA), or the sequence of amino acids in a polypeptide macromolecule found in living cells (protein) and viruses; also any subsequence, such as a gene. Sequences are obtained through wet lab analyses called sequencing. Longer sequences are usually derived by generating short fragments called reads, as in shotgun sequencing, although it is now theoretically possible to sequence an entire chromosome in one read. Reads are assembled together in longer contigs (contiguous regions) by computational methods. As an additional step, another round of sequencing can be done in the laboratory to fill in any gaps and correct errors. After assembly, specialists analyze the sequence(s) to identify its genes and other functional sections of the sequence are identified and characterized. This is called annotating the sequence, and the resulting data attached to the sequence is called the annotation.