Expectation value. The number of different alignents with
scores equivalent to or better than S that are expected to
occur in a database search by chance. The lower the E value,
the more significant the score. (NCBI)
This represents the number of sequences with a score greater-than,
or equal to, X, expected absolutely by chance. The E-value connects
the score ("X") of an alignment between a user-supplied
sequence and a database sequence, generated by any algorithm,
with how many alignments with similar or greater scores that
would be expected from a search of a random sequence database
of equivalent size. Since version 2.0 E-values are calculated
using Hidden Markov Models, leading to more accurate estimates
than before. (SMART)
A method of separating large molecules (such as DNA fragments
or proteins) from a mixture of similar molecules. An electric
current is passed through a medium containing the mixture, and
each kind of molecule travels through the medium at a different
rate, depending on its electrical charge and size. Agarose and
acrylamide gels are the media commonly used for electrophoresis
of proteins and nucleic acids. (ORNL)
Electroporation
A process using high-voltage current to make cell membranes
permeable to allow the introduction of new DNA; commonly used
in recombinant DNA technology.
See also: transfection (ORNL)
Embryonic stem (ES) cells
An embryonic cell that can replicate indefinitely, transform
into other types of cells, and serve as a continuous source
of new cells. (ORNL)
A protein that acts as a catalyst, speeding the rate at which
a biochemical reaction proceeds but not altering the direction
or nature of the reaction. (ORNL)
Epistasis
One gene interfers with or prevents the expression of another
gene located at a different locus. (ORNL)
Escherichia coli
Common bacterium that has been studied intensively by geneticists
because of its small genome size, normal lack of pathogenicity,
and ease of growth in the laboratory. (ORNL)
Eugenics
The study of improving a species by artificial selection;
usually refers to the selective breeding of humans. (ORNL)
Cell or organism with membrane-bound, structurally discrete
nucleus and other well-developed subcellular compartments.
Eukaryotes include all organisms except viruses, bacteria,
and bluegreen algae.
See also: prokaryote, chromosome.
(ORNL)
A short strand of DNA that is a part of a cDNA molecule and
can act as identifier of a gene. Used in locating and mapping
genes.
See also: cDNA, sequence
tagged site (ORNL)
