The ac Locus

Symbol: ac
Also known as: Lethal achondroplasia locus

Squabs expressing homozygous ac (deceased).

Function

A locus associated with a lethal embryonic skeletal abnormality (“achondroplasia”) in pigeons, in which affected embryos show markedly shortened limbs and beak and fail to hatch or do not survive to live birth.

Alleles at this locus

  • ac – Lethal achondroplasia (lethal)
  • ac+ – Wild type (normal)

Inheritance

Autosomal recessive.

Sex linkage was specifically ruled out in Hollander’s study, and the data were consistent with a single autosomal recessive factor. Mating that produced the trait showed an approximate 1:3 achondroplastic:normal ratio (i.e., recessive inheritance). The mutant symbol ac was proposed for the trait.

Primary genetic effects

Affects embryonic skeletal development (a chondrodystrophy/achondroplasia-type defect) leading to non-viability at/near hatching.

Genetic interactions

No specific epistatic interactions were established in the original report; the trait was treated as a developmental lethal rather than a pigment/plumage gene.

Linkage

No linkage was found between achondroplasia and Spread (S) or the white factor(s) tested/observed in the study.

Associated genes / alleles

  • Lethal achondroplasia (ac)

Phenotypes influenced

  • Lethal achondroplasia (embryonic lethal)

Notes and uncertainty

The classic published description is W. F. Hollander (1945), Journal of Heredity 36(10): 297–300.