Neha Patil (Editor)

Polar overdominance

Updated on
Edit
Like
Comment
Share on FacebookTweet on TwitterShare on LinkedInShare on Reddit

Polar overdominance is a unique form of inheritance described in livestock (humans and mice as well), specifically sheep, whereby a mutant Callipyge allele must be inherited from the father to cause muscle hypertrophy. Muscle hypertrophy in the offspring is caused by an increase in the size and proportion of muscle muscle fibers, namely the fast-twitch muscle fibers. This increase is generally located in the hind quarters and torso. Muscle hypertrophy only manifests itself in the offspring approximately one month after birth. Polar overdominance shows evidence of an imprinted locus displayed as the difference between the expression of heterozygote phenotypes in a parent-of-origin type fashion. The term polar is used to desciribe this type of inheritance because the phenotype of one heterzygote is expressed at a level higher than other genotypes for the same locus including those displaying either homozygous geneotype. This unique form of inheritance has largely been studied in non-human mammals since 1996 until it was first described in humans in 2008. In humans, the inheritance of the alleles for the DLK1 gene (imprinted in eutherian mammals) is linked a higher rate of obeseity in the F1 generation. The imprinted DLK1-GTL2 in sheep is homologous to the DLK1 gene in humans, and includes the callipyge locus.

References

Polar overdominance Wikipedia