Consomic or Chromosome Substitution Strains

Definition, Development, and Research Uses

Consomic strains are developed by backcrossing a whole chromosome from one donor inbred strain into a recipient "background" strain. They are used for studying the genetics of complex traits and in the eventual identification of QTLs.51 A minimum of ten backcrosses should be used, though ideally, all the background strain chromosomes should be present and uncontaminated with donor chromosomal fragments (with the exception of the donor chromosome).

The development of Y-chromosome consomic strains is relatively easy. A donor strain male is crossed with a recipient strain, and male offspring are again backcrossed to the recipient strain. This is repeated for ten generations, always using background strain females. Such strains have been used to study the phenotypic effects of genes on the Y chromosome.52

Strains consomic for autosomal chromosomes can now be developed using about five or six polymorphic genetic markers on the chosen chromosome, known to differ between the two strains. Offspring are then only chosen for backcrossing if they have all markers of the donor type for the chosen chromosome, i.e., if the chromosome has not recombined due to crossing over. A full set of consomic strains for the mouse would involve 21 strains, with 19 of them being the background strain with each of the 19 autosomes substituted and the other two being the background strain with either the X or Y chromosome from the donor strain. However, even a few of these strains can be used to answer questions about whether or not there are loci on a particular chromosome that influence a particular phenotype. For example, a number of consomic rat strains with chromosomes from BN strain rats substituted on an SS background have been developed. The background strain has high blood pressure when placed on a high-salt diet. These strains are now being characterized for 203 heart, lung, vascular, and blood function phenotypes. Strain SS.BN-13, for example, which has the BN chromosome 13 substituted, has lower mean arterial pressure than the SS strain, showing that there is a salt-related blood pressure gene on this chromosome.53 In mice, these strains have been used to study susceptibility to germ-cell tumors in 129 strain mice, using a chromosome 19 substitution strain.54

Consomic strains will provide a powerful new set of genetic tools for studying quantitative trait loci as soon as they become more widely available. They provide the opportunity of mapping loci with quite small phenotypic effects, because sample size can be as large as needed to detect any effect thought to be of biological significance.55 One note of caution is that QTLs may interact with one another, so that a difference seen on one genetic background may not be observed with a different background.

Maintenance of Consomic Strains

Once backcrossing is completed, each consomic strain is an inbred strain in its own right and should be maintained in the same way as an inbred strain, as discussed above.

Nomenclature of Consomic Strains

Consomic strains of mice are officially designated by RECIPIENT STRAIN-CHROMOSOME DONOR STRAIN' For example, C57BL/6J-YAKR is a consomic strain with the C57BL/6 autosomes, but the Y chromosome from strain AKR.

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Blood Pressure Health

Your heart pumps blood throughout your body using a network of tubing called arteries and capillaries which return the blood back to your heart via your veins. Blood pressure is the force of the blood pushing against the walls of your arteries as your heart beats.Learn more...

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