**1.1. Sequence annotation tools**

Genome databases accessible via web browsers are very useful in the search for annotation information for DNA sequences. The UCSC Genome Browser web application has been a huge development of great value in analyzing and characterizing sequence information [6]. The application includes a variety of genomic tracks, assemblies, and browsers with genetic information from a host of species. The UCSC Genome Browser, with its various functionalities and annotation options, offers a one-stop shop for researchers, who can work directly on the web application by uploading their data, or they can download source codes of interest from the UCSC Genome Browser and run those locally. Despite its power, however, the main limitation we see in using the UCSC browser for sequence annotation lies in the limited amount of data that can be accessed at a given time, along with the need for human intervention. For example, it is time-consuming for geneticists who want annotation across multiple variant sites at once over different functional classes to use the browser comfortably. Ensembl is yet another superb broad-based web application with an expansive database, offering researchers choices on extracting specific regions of interest and annotating particular regions in the genome [7]. This application has various functionalities and tools that can accept uploaded data, convert formats of documents, and search for sequences of interest; still, like the UCSC browser, it is not the best choice for performing high-throughput sequencing annotation.

SNPnexus is a genetic variation tool developed to help determine functionally relevant SNPs for a given genomic region [8]. It has a user-friendly web interface that accepts inputs in the form of genomic positions, dbSNP id, or chromosomal region. The application database includes two different human genome assemblies: the hg19 and hg18 builds. SNPnexus generates calls on genomic mapping of variant sites, protein function consequences of such variants in the genome, the regulatory elements conserved within the region, and the conservation score of the variant site. The application also provides the genotype and allele frequencies estimation for known SNPs using data from the HapMap Project. This annotation tool, like so many others, is very useful for human variant annotation; however, it does not characterize variants in other species.

Since the development of SeqAnt in 2010, other software tools have come along to perform sequence annotation. Segtor is a tool designed to annotate large sets of genomic coordinates, intervals, single nucleotide variants (SNVs), indels, and translocations [9]. A more recent and very closely related annotation tool is AnnTools [10]. This is an open source web application that accepts user Inputs and queries their database for a full spectrum of variant site annotation, including single nucleotide variants, insertions and deletions, structural variants, and copy number variants. The application has a minimal memory footprint and likewise annotates variants quite rapidly. Nevertheless, AnnTools is restricted to human genome variant annotations and in this sense differs from SeqAnt, which annotates other species besides humans. There are also a number of other variant site annotation tools available either as downloadable command line applications or user interface web applications; these include snpEff (http://snpeff.sourceforge.net), MU2A[11], and Snat [12].
