Type of Strain
- Wild-Derived Strains - Strains formed by inbreeding or other breeding procedures from mice
originally caught in the wild.
- Recombinant Inbred Strains - inbred lines, each derived independently from an F2 generation
produced by crossing two unrelated, inbred progenitor lines.
- Recombinant Congenics - Strains formed by crossing two inbred strains, followed by a few
backcrosses to one of the parental strains, with subsequent inbreeding without selection.
- Coisogenics - Designating inbred strains of organisms that differ from one another only by a
single gene as the result of mutation.
- Congenics - Strains generated by repeated backcrossing (at least 10 generations) that differ from one another only
with respect to a small chromosomal segment. Many congenic mouse strains differ only in a
segment containing the major histocompatibility complex.
- Consomics - Strains derived by repeated backcrossing while maintaining one whole donor chromosome
genetically different from the background strain.
- Unclassified - Stocks that cannot be classified into any of the above categories or
have not yet been classified.
- Non-Inbred - Strain propagated by random mating; could have different genes/genetic
backgrounds introduced from generation to generation.
- Inbred - A group of organisms so highly inbred as to be genetically identical, except for
sexual differences. Brother sister matings have been maintained for 20 or more generations.
- Closed Colony Random Bred - Strain propagated by random mating within stock. No genes
introduced from outside the strain from generation to generation.
- Segregating Inbred - an inbred strain with forced heterozygosity at a particular locus.
- Transgenic - animals into which cloned genetic material has been experimentally transferred.
Type of Mutation
- Deletion - Interstitial loss of a sometimes, but not always, cytologically
visible segment of genetic material from a chromosome. A multilocus deletion involves more than a
single locus, such that adjacent genetic material constituting a part of, or the whole, neighboring
locus or loci has also been lost. An intragenic deletion involves one or more adjacent nucleotides
within a gene and may result in a frameshift mutation, loss of one or more exon sequences, or loss
of regulatory regions that may not be involved in the coding sequence.
- Duplication - A sometimes, but not always, cytologically visible doubling of a section
of the genome. The duplicated segment may be contiguous with the original one (tandem duplication),
contained elsewhere in the same chromosome (intrachromosomal duplication), or incorportated in a
nonhomologous chromosome (interchromosomal duplication).
- Insertion - A type of translocation in which an interstitial segment from one chromosome
(resulting from two breaks) is inserted within a nonhomologous chromosome at a third breakpoint.
A transgene insertion involves genetic material derived from another organism, introduced by
pronuclear microinjection of DNA or incorporation of exogenous DNA by embryonic stem cells
(either by viral infection or electroporation), and incorporated into a host chromosome at a
random or targeted location.
- Intragenic Mutation - A mutation of any of a number of possible, but as yet
undetermined, types within the sequence of a single gene (e.g., single base-pair change,
intragenic deletion, intragenic inversion). An intragenic mutation known (or presumed)
to be the result of a single base-pair change is designated a point mutation (q.v.)
- Inversion - Reversal of a chromosome segment and the gene sequence contained therein.
In a pericentric inversion, the inverted segment includes the centromere; while in a paracentric
inversion, both breakpoints are located in the same chromosome arm. An intragenic inversion involves
reversal of a sequence of nucleotides within a gene.
- Knock-In - A mutation, generated by homologous recombination in embryonic stem cells,
resulting in (usually) a null allele for the gene under study but also resulting in the
incorporation of an easily assayed reporter gene (e.g., lacZ or Green Fluorescent Protein)
that is now under the control of the target gene's normal regulatory sequence.
- Knock-Out - A mutation generated by homologous recombination in embryonic stem cells
and resulting in a null allele for the gene under study.
- Point Mutation - As used in this database, point mutation refers to a single base-pair
change.
- Rearrangement - A change in the usual order and arrangement of genetic material either
within the chromosome complement or within a gene locus. Where the nature of the rearrangement
has been determined, the type may be searched for directly under the following designations:
reciprocal translocation (q.v.), Robertsonian translocation (q.v.), insertion (q.v.),
transposition (q.v.), inversion (q.v.), deletion (q.v.), and duplication (q.v.).
Rearrangements whose nature has not been determined may be searched for under the
"Rearrangement" category.
- Reciprocal Translocation - Reciprocal exchange of segments between non-homologous
chromosomes. Note that usually only symmetrical exchanges can be propagated. Asymmetrical exchanges
result in dicentric and acentric chromosome products that are lost, leading to aneuploid
conceptuses that fail to survive. Reciprocal translocations may involve more than two chromosomes,
e.g., 1/2, 2/3, 3/1.
- Robertsonian translocation - A chromosome structural change resulting from centric fusion
or centric fission, and resulting in two non-homologous chromosomes attached to the same centromere.
- Single-Locus - A mutation that may either be intragenic (q.v.) of an as yet undetermined type,
or may involve deletion of the entire gene locus in question.
- Translocation - Results from an exchange of segments in non-homologous
chromosomes.
- Transposition - Transfer of a chromosome segment to another location either within the
same chromosome (=shift) or to a nonhomologous chromosome (see Insertion).
- Induced - A mutation discovered among the descendants of a mouse whose germ cells,
exposed to a physical or chemical agent, contributed to the conceptus that presumably carried
(though did not necessarily exhibit) the mutation. (There is a very small, but finite, chance
that the mutation could have occurred independent of the mutagen exposure, i.e., be of
spontaneous origin.)
- Spontaneous - A mutation discovered among the descendants of a mouse whose germ cells
were not exposed to a chemical or physical mutagen. Additionally, certain mutants that had a
mutagen-treated parent or ancestor have been concluded to be of spontaneous origin if the germ-cell
stage being sampled is not that which has been exposed, or if the mode of inheritance cannot account
for appearance of the mutant. These special circumstances for certain specific alleles are
explained under Additional Remarks.
Back to Top of Page
Genetics Glossary links:
[an error occurred while processing this directive]