BLAST finds similar sequences but similarity isn't necessarily homology.
For nucleotide the percentage of identity is at least 70%, while for proteins is at least 25%, but usually you need to compare the 3D structure of your proteins against your reference to obtain an idea of the homology. As the previous comment, a good way to study homology in proteins is focus on specific domanis that you are able to find during a blast or blastp.
Homology is strictly linked to similarity (specially for proteins), but it depends on the aim of your work. There are many different free tools online usefull to have an idea, based on your sequences, on the homology of your proteins and potentially to understand the function of them.
Regards.
Hi,
In addition to using BLAST, I would recommend looking up some of the available phylogenetic databases. They rely on different types of data / algorithms and this can help you with your hypotheses.
Databases like http://orthodb.org/? and http://www.ncbi.nlm.nih.gov/homologene.
You can access additional databases from the Uniprot website:
(e.g. for Runx1) "Phylogenomic databases" part of
http://www.uniprot.org/uniprot/Q01196
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