Question: Similarity Score Increase Or Decrease After Translation In Blast
gravatar for Jo- Carpe Diem
4.4 years ago by
Jo- Carpe Diem0 wrote:

Hi, I have a query regarding BLAST specifically blastn and blastx, Why may similarity scores go UP or DOWN after translation ? For example, the percent identity for a sequence in basic blast is 99% whereas in blastx the score is 100%. Why, what causes the change..Why is this please ? I would very much appreciate a detailed explanation please. Thank you

blastn • 1.8k views
ADD COMMENTlink modified 2.5 years ago by Biostar ♦♦ 20 • written 4.4 years ago by Jo- Carpe Diem0
gravatar for Neilfws
4.4 years ago by
Sydney, Australia
Neilfws48k wrote:

Simple answer: the genetic code.

The same amino acid may be encoded by different codons. So for example, a query sequence may contain CCC, the subject sequence CCA. Not identical at the nucleotide level but when translated to protein, both codons encode proline, so identical as protein sequence.

ADD COMMENTlink written 4.4 years ago by Neilfws48k

Thank you! It's always the simplest things that get us thinking

ADD REPLYlink written 4.4 years ago by Jo- Carpe Diem0
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