Strain Type

Description

Advanced intercross line

Advanced intercross strains are made by producing an F2 generation between two inbred strains and then intercrossing in each subsequent generation.

Chromosome altered

In this category, rat strains are grouped by alteration in the chromosome.

Coisogenic

These are inbred strains that differ at only a single locus through mutation occurring in that strain.

Congenic

Congenic strains are produced by repeated backcrosses to an inbred strain with selection for a particular marker from the donor strain.

Conplastic

Conplastic strains are strains in which the nuclear genome from one strain has been crossed onto the cytoplasm of the other (the mitochondrial donor is always the female parent) during the backcrossing program.

Consomic

Consomic strains are produced by repeated backcrossing of a whole chromosome onto an inbred strain.

Hybrid

These are progeny of two inbred strains, crossed in the same direction, and are genetically identical.

Inbred

An inbred strain has a defined background. It has been mated brother x sister for 20 or more consecutive generations, hence these can be traced back to their common ancestors.  Any individual inbred rat’s genome is understood to have on average only 0.01 residual heterozygosity (excluding any genetic drift).  Therefore, members of an inbred strain are regarded for most purposes as genetically identical. An inbred strain is designated by a brief symbol made up of upper case, roman letters or a combination of letters and numbers. Examples of some inbred strains are: ACI, FHH, BN.

Mutant

These are animals in which there is a structural change in the DNA. This could be an insertion, deletion or chromosomal rearrangement generated spontaneously or by artificial methods.

Outbred

These animals are genetically undefined, that is, these are bred with animals that are unrelated to each other, and not bred with siblings or close relatives.

Recombinant inbred

These are formed by crossing two inbred strains, followed by 20 or more consecutive generations of brother and sister mating.

Segregating inbred

These are inbred strains in which a particular allele or mutation is maintained in a heterozygous state.

Transchromosomal strain

Transchromosomal strains carry a chromosome, chromosomal fragment, or engineered chromosome from another species existing as a separate, heritable, freely segregating entity or is centromerically fused to an endogenous chromosome.

Transgenic

These animals have a DNA fragment that has been stably introduced into the germline which can be generated by a random insertion into the genome.

Wild

Rats captured in the wild.