ALLELIC SERIES An array of possible mutant forms of a gene, which usually causes multiple phenotypes.

AMPULLA A swelling at the base of the semicircular canals, which contains sensory cells that detect the movement of fluid inside the canals.

CRE/LOXP A site-specific recombination system derived from the Escherichia coli bacteriophage P1. Two short DNA sequences (loxP sites) are engineered to flank the target DNA. Activation of the Cre recombinase enzyme catalyses recombination between the loxP sites, which leads to the excision of the intervening sequence.

ELECTROENCEPHALOGRAPHY (EEG). This technique measures neural activity by monitoring electrical signals from the brain that reach the scalp. EEG has good temporal but relatively poor spatial resolution.

ELECTROMYOGRAPHY (EMG). A technique used to measure striated muscle activity by monitoring electrical signals from a surrounding group of muscles. In sleep studies, EMG activity, in combination with electroencephalography, determines behavioural states, wakefulness, rapid eye movement (REM) and non-REM sleep.

FEAR CONDITIONING A test to measure the ability of a rodent to learn and remember an association between an aversive experience and environmental cues. Learning and memory are assessed by scoring freezing behaviour in the presence of the cue or context.

FORWARD GENETICS A genetic analysis that proceeds from phenotype to genotype by positional cloning or candidate-gene analysis.

LONG-TERM POTENTIATION A long-lasting increase in the efficacy of synaptic transmission, which is commonly elicited by high-frequency neuronal stimulation.

ORGAN OF CORTI The structure in the inner ear that contains receptor cells that are sensitive to sound vibrations.

PLEIOTROPY The phenomenon in which a single gene is responsible for several distinct and seemingly unrelated phenotypic effects.

PREPULSE INHIBITION OF THE STARTLE RESPONSE A behavioural test for sensorimotor gating. This task measures the level of attenuation of a startle response on presentation of a non-startle-inducing prepulse.

QUANTITATIVE TRAIT A measurable trait that depends on a single gene or on the cumulative action of many genes and the environment.

QUANTITATIVE TRAIT LOCUS (QTL). A genetic locus that is identified through the statistical analysis of complex traits (such as height or body weight). These traits are typically affected by more than one gene and also by the environment.

REVERSE GENETICS A genetic analysis that proceeds from genotype to phenotype by gene-manipulation techniques, such as homologous recombination in embryonic stem cells.

SENSORIMOTOR GATING A behavioural trait in humans and animals that reflects the ability to filter out extraneous stimuli and to process information that comes in rapid succession.

STEROID-HORMONE-REGULATED CRE Cre recombinase that has been engineered to contain mutated progesterone or oestrogen ligand-binding domains that are specifically bound by synthetic steroids. This binding allows Cre to be translocated to the nucleus.