IITS course on
KU Leuven, Spring 2013
Lecture 2
Evolving Populations (backward
Kolmogorov)
- Steady states:
- For general drift/diffusion
- For population with mutations/drift/selection
- The bacward Kolmogorov equation:
- Steady states with absorbing states
- Derivation of the backward Kolmogorov equation
- Fixation:
- General solution of the backward Kolmogorov equation
- Fixation probability with selection
- Fixation probability of a new mutation
- Mean first passage times:
- Mean time to fixation
- Mean time to loss
- Mean survival time
Sequence Comparison
- Sequence comparison
- Protein sequences: amino acids and their
properties
- Why do we need to compare sequences?
- Find dissimilarities
- Similar sequences = similar properties
- Similar sequences
= common ancestral genes
- Mutations -> Gapless alignments
- Mutations, insertions and deletions -> Gapped alignment
- Sequence alignments
- Score
= edit distance
- Examples of scores
- Length of alignment, number of alignment
- Substitution Matrices (PAM)
- Algorithms for sequence alignments
- Dynamics programming
- Example
- Global and Local
- Advanced Dynamic Programming Tutorial
- BLAST
- How it works
- Examples
Significance of Aligned Sequences
- Sequence
alignment (Wikipedia applet)
- Inputs:
- Explicit- Two sequences {a1, a2,
...., am} and {b1, b2, ...., bn}
(e.g. query and database)
- Implicit- A scoring procedure, e.g. pairwise scores s(ai,bj)
and gap costs
- Alignment algorithm: global, local, gapped, gapless (dynamic programming, applet)
- Output: matching (sub)sequences with an overall score S
. (example)
- Significance: What is the probability of getting a score S by
chance?
- Statistics of gapless local alignments:
- Gapped alignments and Statistical Physics
[Lecture Notes]
[Exercises]
Related links
IITS
lec2- last update 5/27/13 by
M. Kardar