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MEDEA = Maternal-Effect Dominant Embryonic Arrest

Medea factors all share several characteristics:
  • They breed true through the female line.
  • They segregate in the male.

When a heterozygous Medea female (M/+) is crossed to a wild type male (+/+), the M gene and its homolog segregate normally. However, all progeny that do not inherit the Medea allele die at or shortly after egg hatch. The lethality is maternal, but the "rescue" is zygotic. The rescuing M allele can be inherited from either parent.

There have been four well-studied Medea factors. Of these, two (M-1 and M-4) are currently maintained at the Tribolium Stock Center. Almost all M strains in the field carry M-4. Of these, about a third also carry M-1. M-4 is the only Medea factor present in North American and European strains, being found in about half of them. Australian and Indian strains are almost devoid of Medea factors. South American, Asian, and African strains often have 2 or more M factors.

phot of Medea-killed larvae

 
M-1 = Medea-1
Gene: Medea-1
Feature/structure: Incompatability w/ H gene; selfish gene
Linkage Group:   3  
Origin: spontaneous
 
M-4 = Medea-4
Gene: Medea-4
Feature/structure: Incompatability w/ H gene; selfish gene
Linkage Group:   3  
Origin: spontaneous