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Sequence Analysis Alan Christoffels alan@sanbi.ac.za.

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Presentation on theme: "Sequence Analysis Alan Christoffels alan@sanbi.ac.za."— Presentation transcript:

1 Sequence Analysis Alan Christoffels

2 Sequence Analysis Alignments dot-plots scoring scheme Substitution matrices Search algorithms (BLAST)

3 What is a sequence alignment??
S O U T H A F R I C A S O O T H A F R I C A

4 What is a sequence alignment??
S O U T H A F R I C A S O O T H A F R I C A

5 What is a sequence alignment??
S O U T H A F R I C A S O O T H A F R I C A S O U T H A F R I C A S O U T H A F R I K A

6 What is a sequence alignment??
S O U T H A F R I C A S O O T H A F R I C A S O U T H A F R I C A S O U T H A F R I K A

7 What is a sequence alignment??
S O U T H A F R I C A S O O T H A F R I C A S O U T H A F R I C A S O U T H A F R I K A S O U T H A F R I C A S O U T - A F R I C A

8 What is a sequence alignment??
S O U T H A F R I C A S O O T H A F R I C A S O U T H A F R I C A S O U T H A F R I K A gap S O U T H A F R I C A S O U T - A F R I C A

9 Uncertainty in alignments
S O T H A F R I C A S O O T H - F R I K A N S - O T H A F R I C A S O O T H - F R I K A N

10 Gaps, Insertions & deletions (indels) and substitutions
S O U T H A F R I C A S O U T H R I K A N gaps

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12 End-to-end Not aligned

13 Why do we want to compare sequences??
Predict functions of unknown sequences; find gene families

14 Why do we want to compare sequences??
What is underlying hypothesis when you predict a function by comparing two sequences ????? Predict functions of unknown sequences; find gene families

15 Why do we want to compare sequences??
Predict functions of unknown sequences; find gene families

16 Why do we want to compare sequences??
Predict functions of unknown sequences; find gene families Positions not critical to function can mutate randomly!!!!!

17 Why do we want to compare sequences??
Predict functions of unknown sequences; find gene families Find an example where the above is not necessarily true

18 Sequence Comparisons similarity due to a common ancestor
Homology similarity due to a common ancestor no degrees of homology Predict functions of unknown sequences; find gene families

19 Sequence Comparisons Predict functions of unknown sequences; find gene families

20 Sequence Comparisons Predict functions of unknown sequences; find gene families

21 Sequence Comparisons Predict functions of unknown sequences; find gene families

22 Sequence Comparisons Predict functions of unknown sequences; find gene families

23 Sequence Comparisons Dot-plots
Predict functions of unknown sequences; find gene families

24 Dot - plots One sequence compared to another. Identify regions of similarity

25 Dot - plots One sequence compared to another. Identify regions of similarity

26 One sequence compared to another. Identify regions of similarity

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34 What do palindromes look like in a dot-plot????

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42 Scoring Path


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