J. A. Fraser Roberts
Articles written in Journal of Genetics
Volume 14 Issue 3 December 1924 pp 367-374
Volume 17 Issue 1 August 1926 pp 77-83
A brief description is given of the Piebald breed of sheep. While there is a considerable range of variation in the extent and nature of the spotting these sheep breed remarkably true for the piebald character.
The-result of crosses with other breeds is the production of self-blacks.
A back-cross of the F1 to white gave six whites and five blacks. A back-cross of the F1 to piebald gave sis piebalds and four blacks.
Piebald sheep differ from other breeds in that they possess a dominant black factor and a recessive pattern factor which restricts the black to certain areas.
Volume 19 Issue 2 January 1928 pp 261-268
A type of pigmentation in sheep is found in which the derivatives of the primitive outer coat-face and leg hair, kemp, and birth-coat-are coloured and the body of the fleece practically free from colour.
Variations in face colour fall into three groups:
Those affecting the relative proportions and distributions of coloured, and white fibres.
Those affecting the dilution of this pigment.
Those affecting the precise degree of restriction of pigmentation in the white-faced sheep; this pigment being mainly confined to the skin.
A further analysis of the results of T. B. Wood in his crosses of Suffolk and Dorset Horn sheep shows that these results can be explained on the basis of a two-factor difference, the variations in this case being of group 1.
As a working hypothesis, it is suggested that the above classification, together with the recognition that variations of group 1 are mainly due to the different states of two factors, affords a reasonable explanation of the variations in face colour found in the white-fleeced breeds of sheep and in their crosses.
Volume 21 Issue 1 April 1929 pp 57-69
A lethal deformity of new-born lambs is described. The most striking feature of the condition is that the lambs are born with some or all of the limbs rigidly fixed, with only a small degree of movement possible at the joints. Parturition is rendered very difficult and there is a considerable mortality amongst the ewes producing these lambs.
The condition depends upon the homozygous state of an autosomal recessive factor.
During two years the sex-ratio of the affected lambs born in the flock observed was abnormal. Subsequent results and in particular an
The incidence of the defect is discussed and a brief account is given of the history of its appearance in the particular flock observed.
Volume 22 Issue 2 May 1930 pp 165-180
Volume 22 Issue 2 May 1930 pp 181-190
Further data are given on the inheritance of the dominant black of the Black Welsh Mountain breed.
Results are given that have a bearing on the question of the origin of dominant blacks and the inter-relationship of the dominant blacks of various breeds. It is possible that more than one factor exists that can produce dominant black.
It is shown that in the presence of the dominant black factor the factors for badger-face pattern and reversed badger-face pattern cannot be expressed.
A brief account is included of some of the modifications of black colour.
A very brief summary is given of the present state of knowledge regarding the genetics of coat colour in the sheep.
Volume 25 Issue 1 November 1931 pp 1-16
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