Sequence analysis

3 important questions on Sequence analysis

What type of questions can be answered with using BLAST?

Studying the absence or presence of idividual genes

Aligment score is given by bit-score or percentage. What does identities and positives mean in this aspect?


• Identities: % of how similar they are
• Positives: % of how identical they are

What is the E-value used for and what does it say about the hit?

Chance of finding a hit with a high score by random chance. This increases if you use a larger database --> must be corrected by:  expect (E-value)
Depends on alignment score(s), lengths of query (m), size of database.

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