Categories: All - alignment

by nurul izzati 11 years ago

420

pairwise sequence alignment

Pairwise sequence alignment is a crucial method in bioinformatics used to identify regions of similarity that may indicate functional, structural, or evolutionary relationships between sequences.

pairwise sequence alignment

Pairwise Sequence Alignment

sequence alignment

gaps #
gap penalties

extension

opening

deduction for gaps

G + Ln

for insertion & deletion
to improve alignment between two sequence
identity and similarity
quantitative inference
homology
orthologs

common ancestor

paralogs

gene duplication

alignment algorithms

local sequence
BLAST

component

4. choose optional parameter

3. choose database

nucleotide sequence database

protein sequence database

2. select BLAST programme

types

tblastx

translated nucleotide --> translated nucleotide

tblastn

protein --> translated nucleotide

blastx

translated nucleotide --> protein

blastp

protein --> protein

blastn

nucleotide --> nucleotide

1. choose query

accession number

FASTA format

best for sequence that share some similiraty or different length
region of greater similarity
global sequence
best for highly similar of sequence similar length
entire length of sequence

scoring matrices

TYPES
BLOSUM

BLOSUM 30

longer weaker local alignment

BLOSUM 80

detect known member of protein family

BLOSUM 62

most effective in finding potential similarities

BLOSUM 90

short alignment, highly similar

perform better than PAM

most sensitive detect structural of functional substitution

directly calculated, no extrapolation

PAM

Dayhoff Model

to compare divergent proteins compute

based on global alignment of closely related proteins