Attenuation in bacterial gene regulation regulates downstream transcription through formation of alternative RNA structures during transcription. In the tryptophan example, biological translation of a leader peptide influences which structure forms; the immediate decision is transcription termination.

A regulatory factor that helps a transcription activator increase target gene expression, often through interactions with chromatin or the RNA polymerase machinery.

A regulatory factor that helps repress target gene expression through recruited molecular interactions. The outcome depends on the bound regulator, promoter and cellular context.

Control over when, where and how much a gene is expressed. Evolutionary changes in expression domains can alter developmental identity without requiring movement of a formed organ.

Regulation through a diffusible product acting at another genetic locus, contrasted with a local cis-regulatory sequence.

Differential gene expression is a difference in expression between specified biological conditions or biological populations. A comparison must define the measured quantity, such as transcript abundance or protein production. Increased abundance can arise from increased synthesis or decreased removal, and mixed tissues can change through altered cell composition. Replication and a suitable statistical model are needed to separate a reproducible difference from sampling variation. ^[ref]

A relationship between genes arising through duplication. It differs from orthology, which concerns divergence through lineage splitting.

Gene-family evolution through duplication and retention of some copies and loss or pseudogenization of others.

A tandem duplication creates an additional copy of a genomic segment adjacent to the original. A duplicated gene can initially increase dosage, after which the copies can diverge or one can lose function. Adjacency distinguishes tandem copies from duplicates moved to distant positions. Repeated near-identical copies can also complicate genome assembly because short sequencing reads may not identify which copy they came from. ^[ref]

Creation of adjacent copies of a gene or genomic segment. Subsequent divergence can produce a local gene family while preserving aspects of ancestral order.

Duplication of the full genomic complement. gene loss, subfunctionalization and neofunctionalization can obscure the original duplicated organization.

A bias in transmission or repair favouring G/C over A/T at suitable heterozygous sites. It can produce substitution patterns resembling selection without a corresponding organism-level fitness advantage.

An antheridium is a structure that produces male gametes in relevant plant and other lineages. In bryophytes and many ferns, antheridia on the gametophyte produce motile sperm.

A suitable water connection allows those sperm to reach an archegonium. Release and transport of spores can occur under different conditions, so efficient spore dispersal does not remove the later water requirement for fertilization.

An archegonium is an egg-producing reproductive structure in several land-plant lineages, including bryophytes and many ferns. It belongs to the gametophyte generation and contains the ovum reached by sperm during fertilization.

After fertilization, the developing sporophyte can remain associated with the maternal gametophyte. This links reproductive anatomy to maternal support of a new generation without making the two generations one genetically identical individual.

A name commonly used for a fern gametophyte. A small photosynthetic free-living body is a useful example, but not a description of every fern gametophyte.

An impartial game is a game in which both players have the same legal moves from any given position. Under the normal-play convention, a player with no legal move loses. For finite games without draws, Grundy numbers encode positions for the Sprague-Grundy theorem.

The convention that a player unable to move loses. In a finite impartial game without draws, a position is winning exactly when it has a move to a losing position.