Inheritance Patterns of Coat Colouration and Horn Number in Jacob Sheep

Abstract

The allele for black coat colour is dominant relative to the allele for lilac in Jacob sheep and is affected by a single gene locus. The percentage of this colouration, as opposed to white fleece, across the body has a heritability value of 0.255. The mode of inheritance for horn number in these animals is less clear, with neither the trait for 2 horns, nor for 4 horns being totally dominant, based on crosses of 2 x 2-horned parents and 4 x 4-horned parents; although in these examples the majority of lambs had the same number of horns as their parents. However, when one parent had 2 horns and the other had 4 horns, the gender of the 4-horned parent appeared to influence the frequency of 4-horned offspring; 77% of lambs born to a 4-horned dam being 4-horned, but only 50% when the 4-horned parent was the sire. These data suggest evidence for sex-limiting factors being involved in determining the number of horns in this breed.

Keywords

• jacob sheep
• horn number
• coat colour