254

Epidemic  see Pandemic. 

E-value  Statistical parameter that indicates whether my output alignment will be found

again in the database with a similar or better score (expected value of a random hit; should

be less than 1 in 1 million). It is therefore dependent on the size of the database (in contrast

to the p-value).

Evolution  (from Latin evolvere, “to develop”) deals with the gradual changes over time

(typically long periods of time up to millions of years) of genetic material and external

appearance in individuals, populations, species up to entire ecosystems. When genetic

material is passed on for the next generation during cell division, there are sometimes

minor or major changes in the genetic material in addition to identical copies of the genetic

material. The resulting appearance of the body (phenotype) may be better, worse, or

equally adapted to the currently prevailing environment as a result of these genetic changes.

Random changes (mutations), natural selection and reproduction (replication) work

together to achieve this. Depending on the environment, a mutation can thus be advanta­

geous, disadvantageous or insignificant (neutral).

ExPASy Server  This is the most famous website of the Swiss Bioinformatics Institute,

an expert system for protein sequence analysis (ExpertProteinAnalysis System). It is an

example of a portal, i.e. a website where you can find numerous databases and software.

For example, I can use different software options to check whether my protein sequence is

really the enzyme I think it is (for example, if it is the BLAST result). The database and

software PROSITE checks whether all the important catalytic amino acid residues are

present or “peptide properties” checks whether the amino acid composition matches the

protein, for example, whether the protein has enough hydrophobic amino acids to fit into

the membrane.

False Positive Hits  Proportion of hits that are grouped incorrectly (e.g., potentially pre­

dicted interaction partners that are not experimentally validated or person grouped as sick

but who are actually healthy).

FASTA  Storage format (text-based) of bioinformatics for sequences, such as gene

sequences.

Feedback Loops  positive/negative feedback loops. 

First Gödel’s Incompleteness Theorem  Proves that there are always unprovable state­

ments in sufficiently strong contradiction-free systems (computer thus remains in the

undecidable).

Genetic Drift  Random sequence change that can affect the function, e.g. of catalytic

domains or functional sites. Stronger moves (e.g. insertion, deletion, clear direction) are

called genetic shift and can lead e.g. to virus subtypes (e.g. in influence). 

18  Glossary