Viewing a single comment thread. View all comments

iayork t1_ja80u83 wrote


In sheep and pigs, there’s a complex scenario (“polar overdominance”) in which only heterozygotes with a particular mutation show the phenotype:

> A single nucleotide polymorphism in the DLK1-DIO3 imprinted gene cluster alters gene expression … muscle hypertrophy only occurs in heterozygous animals that inherit a normal maternal allele and the callipyge SNP on the paternal allele (+/C).

New insights into polar overdominance in callipyge sheep

The details of how this works don’t seem to be well understood and I’m not going to try to summarize the complicated tentative explanations. In sheep and pigs, the muscular hypertrophy phenotype is at least somewhat desirable, but in humans there may be a similar mutation that, in heterozygotes, is associated with severe obesity.

> In a study sample of 1025 French and German trio families comprised of both parents and extremely obese offspring we found a single nucleotide polymorphism (rs1802710) associated with child and adolescent obesity. Analysis of the allelic transmission pattern indicated the existence of polar overdominance, an unusual mode of non-mendelian inheritance in humans previously known from the callipyge mutation in sheep.

Preferential reciprocal transfer of paternal/maternal DLK1 alleles to obese children: first evidence of polar overdominance in humans


Tus3 t1_ja8cr7j wrote

Your post mentioned overdominance, which made me look up the term on Wikipedia.

That led me to the article for underdominance:

This made me wonder, does one of the examples on that page fit the OP's question?


Jrj84105 t1_ja8gski wrote

This is region so highly conserved. The imprinting of genes on both the maternal and paternal alleles makes any genetic chaos here quite deleterious.