Kategóriák: Minden - database - mutations - scores - alignment

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Pairwise sequence alignment

The text delves into the methods and tools used for pairwise sequence alignment in bioinformatics, focusing on the use of scoring matrices such as PAM and BLOSUM. It describes how these matrices are employed to assess the similarity between protein sequences, with PAM1 representing a 1%

Pairwise sequence alignment

Pairwise sequence alignment

SCORES

scores
bit scores (normalized scores)
raw scores (calculate from substitution matrix)
gap penalty
extension - elongate gap
opening - inroduce gap
mismatch
identity

SCORING MATRICES

BLAT
more than 95% similarity
design to rapidly align longer nucleotide sequence
500 times faster than BLAST
BLAST-like alignment tool
BLAST
Smith-Waterman local alignment

CHOOSE optional parameters

output format

word size

expect value

E = Kmn e-λS

Extreme Value Distribution (EVD)

substitution matrix

Turn filtering on/off

Organism

different for every blast program

CHOOSE database

pnv_nr

Subtopic

Pat

Pdb

RefSeq

Swisprot

Month

nr

SELECT BLAST program

tblastx

tblastn

blastx

blastn

blastp

CHOOSE sequences

four component for BLAST search

Blocks Substitution Matrix (Henikoff)

X% identical

local alignment (distantly related protein)

PAM
Percent Accepted Mutations (Dayhoff)

global alignment (closely related protein)

X% divergence

PAM1

one PAM (unit of evolution) = 1% amino acids changed between two proteins

at least 85% identical

probability of occurance + percent accepted mutations = mutation probability matrix

MUTATIONS

Mutability

Trp

Cys

Leu

Phe

Tyr

high mutability

Glu

Asp

Ser

Asn,

Can happens by
deletion
insertion
substitution