N30 F1

Figure. 1 Breeding system for producing congenie mice.

that the coisogenic strains differ only by a point mutation. When they are produced the level of probability is defined by the equation:

where p = probability, n = number of generations and c = recombination frequency. The higher the number of backcrosses the smaller the length of the differential chromosomal segment.

Genetics of the donor strains in congenic mice

The majority of the congenic mice were produced in the C57BL6 of C57BL10 mice (Table 1 gives examples of congenic and A mice background).

Symbols

The H2 complex occupies a segment of the chromosome 17 at a distance of some 15 cM from the centromere. The segment is between 0.1 and 1.5 cM long and contains a minimum of 10-15 loci. (The length of the segment and the number of loci in it depend on which loci one counts as belonging to the H2 complex.) To understand the designation of the congenic lines, Table 1 illustrates the strains (background partners) from which they originated with the locations. These are some of the congenic strains that are available today at the Jackson Laboratory in Bar Harbor, Maine.

Congenic strains can be named by the symbols of the parents' strains used in the original mating. They are separated by a period, i.e. B10.D2; this means that BIO originated from C57BL/10SN and D2 from DBA/2J. They can also be designated by using the name of the inbred partner followed by a hyphen and then the name of the differential allele contributed by the donor strain as described.

Numbers and letters in parenthesis are used when several different strains are derived from one initial cross.

There are also symbols that originated for laboratory purposes only but subsequently were used in the literature, i.e. (5M), (HW80), (HW19).

For designation of substrains, the addition of an abbreviation of the laboratory where they originated from is used, e.g.: Sn for Snell and By for Bailey.

When congenic strains differ at nonhistocompati-bility loci, designations are used to distinguish the differential loci; e.g. Ea for erythrocyte antigen, Ly for lymphocyte, Thy for thymocyte and Tla for thymus-leukemia antigen.

See also: Allelic exclusion; Genetic analysis at the phenotypic level; H2 class I; Inbred strains; Linkage

Table 1 Examples of congenie strains

Strain

Genotype*

Donor strain

Congenic strains with differential locus in the H2 complex

A.BY/Sn

H2b Tla?

Non-inbred

A.CA/Sn

H2' Tlaa

Non-inbred

A.SW/Sn

H2S Tlab

Non-inbred

B6.AKR-H-2h/FlaEg

H2k

AKR/JBy

B6.C-H-2d/aBy (HW19)

H2d

BALB/cBy

B10.A/SgSn

H2a Tla"

A/WySn

B10.AKM/Sn

H2m Tlak

AKR.M/oSn

B10.Br/SgSn

H2k Tlaa

C57BR/cdJ

B10.D2/nSn

H2d Tlac He'

DBA/2

B10.HTG/2Cy

H29

HTG/GoSfSn

C3H.HTG/Sn

H29 Tlab?

HTG/Sn

C3H.NB/Sn

H2P Tlac?

Non-inbred

C3H.SW/Sn

H2b Tlab?

Non-inbred

Congenic strains with differential locus at H loci other than H2

B6.H-1b/By (HW80)

H-1b, c, Hbbd

BALB/cBy

B6.C-H-7b/By (HW23)

H-7b, Mod-1a

BALB/cBy

B6.C-H-8°/By (HW96)

H-8C

BALB/cBy

B6.C-H-15c/By (HW13J)

H-15c

BALB/cBY

Congenic strains with differential locus that determines

nonhistocompatibility cell membrane alloantigens

B6.RIII(76NS)/Sn

Ea-2a

Rill

B6. PL-Ly-2aLy-3a/Cy

Ly-2a Ly-3a

PL/J

B6.PL-Thy-1a/Cy

Thy-1a

PL/J

BALB/c-lghb/Smn (C.B-17)ighb

C57BL/Ka

BALB/c-lghd/Smn (C.B-20) lghd

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