Since the [[Phi-X174 phage|Phage &amp;Phi;-X174]] was [[sequencing|sequenced]] in 1977, the [[DNA sequence]]s of more and more organisms have been decoded and stored in electronic databases. This data is analyzed to determine genes that code for [[protein]]s, as well as regulatory sequences. A comparison of genes within a [[species]] or between different species can show similarities between protein functions, or relations between species (the use of [[molecular systematics]] to construct [[phylogenetic tree]]s). <a rel="dofollow" href="http://www.all-auto.ro/dezmembrari-auto" title="dezmembrari masini"><img src="http://www.all-auto.ro/images/dezmembrari auto" alt="dezmembrari masini" hspace="2" vspace="2" border="0" /></a> With the growing amount of data, it long ago became impractical to analyze DNA sequences manually. Today, [[computer program]]s are used to search the [[genome]] of thousands of organisms, containing billions of [[nucleotide]]s.&nbsp; These programs can compensate for mutations (exchanged, deleted or inserted bases) in the DNA sequence, in order to identify sequences that are related, but not identical. A variant of this [[sequence alignment]] is used in the sequencing process itself. The so-called [[shotgun sequencing]] technique (which was used, for example, by [[The Institute for Genomic Research]] to sequence the first bacterial genome, ''Haemophilus influenza'') does not give a sequential list of nucleotides, but instead the sequences of thousands of small DNA fragments (each about 600-800 nucleotides long). The ends of these fragments overlap and, when aligned in the right way, make up the complete genome. Shotgun sequencing yields sequence data quickly, but the task of assembling the fragments can be quite complicated for larger genomes. In the case of the [[Human Genome Project]], it took several months of CPU time (on a circa-2000 vintage DEC Alpha computer) to assemble the fragments.&nbsp; Shotgun sequencing is the method of choice for virtually all genomes sequenced today, and [[genome assembly]] algorithms are a critical area of bioinformatics research.</p>