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What is done in pairwise alignment?
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Two sequences are stuck on top of each others and the common areas lined up
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Two sequences are aligned from the beginning and their similarity analysed
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Two sequences are aligned and their similarity analysed
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Local alignment assigns correspondences to all residues in the sequence, leaving gaps if necessary
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The image shows which of the following?
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The image shows a mismatch
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What can sequence identity be used for?
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DNA sequence
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Amino acid sequence
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Gene sequence
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Sequence identity can be how specific?
Frage 7
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Spaces in part of the sequence that allows other areas to align better
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Areas with a high density of indels
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Proteins that align when sequences are swapped over
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What is the scoring system that determines an optimal alignment?
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+2 Match -1 Indel -2 Mismatch
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+2 Mismatch -1 Match -2 Indel
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+2 Match -1 Mismatch -2 Indel
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Needleman and Wunsch algorithms find the highest scoring path across a matrix
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Which is the light grey, and which is the dark grey?
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PAM matrices used varies depending on the S.I
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PAM250 scoring is used for remote homologues
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In PAM250 scoring, scores are given based on what?
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What does BLAST stand for?
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Basic Loci Alignment Search Tools
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Basic Loci Alignment Sequencing Tools
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Basic Local Alignment Search Tools
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What is different about BLAST techniques?
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The compare residue 'words' instead of single residues/bases
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They work in areas of less than 50bp long
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They cover the whole genome very rapdily
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A 'word' is 3bp or 11 aa long
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Once the words have been found in the sequence, they are compared to the database- why?
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An E value is expectation, not probability
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What is the range and significance for the E value?
Smaller values are more likely
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The E value is the probability of getting a result by change in a database of this size
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What is the difference between P and E values
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Both are values for 'What is the probability of getting this result by chance alone?', but P accounts for database size
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Both are values for 'What is the probability of getting this result by chance alone?', E accounts for database size
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In P values, <0.05 is significant
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P value relies on a normal distribution
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What are the limits of P?
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An E of 4 is equal to - in a database of this size, I could get 4 matches by chance alone