E – Essential Biology Terms and Concepts Explained in our Glossary | Biologyideas.com

Effective population size

The effective number of adults contributing gametes to the next generation.


A small molecule involved in controlling expression of a regulated gene or the activity of a protein.

Elongation factor (EF)

Accessory proteins required for the elongation phase of translation in prokaryotes and eukaryotes.

Embryonic stem (ES) cell

A cell derived from a very early embryo that retains the ability to differentiate into a cell type characteristic of any part of the organism.


A set of gene regulatory elements in eukaryotic genomes that can act over distances up to thousands of base pairs upstream or downstream from a gene. Most enhancers bind activators and act to stimulate transcription.

Environmental genomics

A branch of comparative genomics involving the analysis of genomes in entire communities of microbes isolated from the environment.

Environmental variance

Component of the phenotypic variance for a trait that is due to any nongenetic source of variation among individuals in a population. includes variation arising from general environmental effects, which permanently influence phenotype; special environmental effects, which temporarily influence phenotype; and family environmental effects, which are shared by family members.


Referring to a heritable change in gene expression that does not result from a change in the nucleotide sequence of the genome.


In bacteria, a plasmid that is capable of integrating into the host cell’s chromosome.


Interaction between two or more genes that controls a single phenotype. For instance, the expression of a gene at one locus can mask or suppress the expression of a second gene at another locus.


The specific short region of a protein (or other molecule recognized by an antibody) that is bound specifically by the antibody.

Essential gene

A gene that when mutated can result in the death of the organism.


Chromatin that is condensed during mitosis but becomes uncoiled during interphase, when it can be transcribed.


One of the three major evolutionary domains. Organisms in this domain have genetic material in a membranebound nucleus as well as a number of membrane-bounded organelles such as mitochondria.


Any organism whose cells have a membrane-bound nucleus in which the genetic material is located and membrane-bound organelles (e.g., mitochondria). Eukaryotes can be unicellular or multicellular and constitute one of the three major evolutionary domains of organisms.


Referring to an organism or cell that has one complete set of chromosomes or an exact multiple of complete sets.


Genetic change that takes place over time within a group of organisms.

Evolutionary domains

The three major lineages of organisms—Bacteria, Archaea, and Eukarya—thought to have evolved from a common, single-celled ancestor.

Excision repair

An enzyme-catalyzed process for removal of thymine dimers from DNA and synthesis of a new DNA segment complementary to the undamaged strand.


A segment of a protein-coding gene and its precursor (pre-mRNA) that specifies an amino acid sequence and is retained in the functional mRNA.

Exon shuffling

Proposed mechanism for evolution of genes with new functions by the duplication and rearrangement of exons encoding protein domains in different combinations. Also called exon shuffling.

Expected heterozygosity (He)

The number of heterozygotes expected if the population is in Hardy–Weinberg equilibrium.


Vector A cloning vector carrying a promoter and other sequences required for expression of a cloned gene in a host cell.


The degree to which a particular gene is expressed in the phenotype. A gene with variable expressivity can cause a range of phenotypes.

Extranuclear inheritance

The inheritance of characters determined by genes located on mitochondrial or chloroplast chromosomes. Such extranuclear genes show inheritance patterns distinctly different from those of genes on chromosomes in the nucleus. Also called non-Mendelian inheritance.