What is the purpose of the BLAST tool?

The BLAST (Basic Local Alignment Search Tool) is primarily utilized to compare a nucleotide or protein sequence to a database of known sequences. When a user inputs a sequence into BLAST, the tool searches through a vast repository of genetic data to find regions of similarity or matches, enabling researchers to identify homologous sequences in other organisms or to find variants in their own sequence data. This function is critical in many areas of bioinformatics and molecular biology, including gene identification, functional annotation of genes, and evolutionary studies.

The other options describe processes that are not what BLAST is designed for; for example, manual annotations involve human interpretation of data rather than automated comparisons. Analyzing protein structures often requires different tools focused on computational modeling rather than sequence alignment, and sequencing genomes would more likely utilize technologies and methods specific to sequencing, rather than a comparison tool like BLAST. Thus, understanding that BLAST facilitates the comparison of sequences helps clarify its essential role in bioinformatics.