There are two main types of errors that can occur in this process: false positive and false negative. A false positive occurs when two proteins are incorrectly found to be homologous, while a false negative occurs when one protein is not found to be homologous with another.
What is an example of a false positive?
For example, the BLAST search between “Homo sapiens” and “Bos taurus” returns multiple results, including human growth hormone, which is not homologous to Bos taurus.
What is an example of a false negative?
For example, when BLAST search between “Homo sapiens” and “Bos taurus”, the result will return that there are no hits found. However, this does not mean that HGH is not homologous to Bos taurus because it could be that the sequence size of HGH does not match up with the search parameters.