Table 1.
Glossary
| Breakpoint | A specific site of chromosomal breakage associated with a chromosomal abnormality. |
| Copy number variant (CNV) | A type of genomic variation in which segments of DNA of more than 1,000 base pairs are duplicated or deleted, as genomic risk factor for common complex brain disorders. 22q11.2 microdeletion and duplication are examples of specific CNVs. |
| Endophenotype | A state-independent biomarker or cognitive marker of an illness (present whether or not the illness is active) that is heritable and present in unaffected relatives of subjects that have the illness (108). |
| Epistasis | Interactions between genes in which the contribution of one gene to a phenotype depends on the genotype at another locus. |
| Haploinsufficiency | The situation in which one copy of a gene is incapable of providing sufficient protein production to ensure normal function. |
| Hemizygosity | A genetic condition where there is only one copy of a gene in an otherwise diploid cell or organism. |
| Low copy repeats (LCRs) | Highly homologous sequence elements within the eukaryotic genome arising from segmental duplication. |
| Long-term potentiation (LTP) | A long-lasting enhancement in signal transmission between two neurons that results from stimulating them synchronously. |
| Non-allelic homologous recombination (NAHR) | A form of homologous recombination that occurs in two pieces of DNA that have similar sequences, often as a result of the presence of low copy repeats (LCRs). NAHR can occur within the same LCR or in an alternative LCR, and can result in a variety of chromosomal rearrangements, including deletion, duplication, translocation, and inversion. The presence of LCRs and resultant NAHR is believed to play a key role in molecular evolution in primates, as a mechanism involved in rapidly changing gene dosage (which may be advantageous) and even the creation of new genes (30). |
| Pleiotropy | The phenomenon whereby one gene influences multiple, independent phenotypes. |
| Prepulse inhibition (PPI) | A quantitative trait, readily measurable in humans and in mice, involving reduced magnitude of the startle reflex that occurs when the subject is presented with a weak stimulus, or prepulse, immediately before the startling stimulus is presented. |
| Single nucleotide polymorphism (SNP) | Genetic variation in a DNA sequence that occurs when a single nucleotide - A, T, C, or G - in a genome is altered, which can affect function of the gene product. |