Íslenskar landbúnaðarrannsóknir - 01.03.1970, Page 5

ÍSL. LANDBÚN.
J. AGR. RES. ICEL.
1970 2,1 3-135
Colour inheritance in Icelandic sheep and relation between
colour, fertility and fertilization1
Litaerfðir í íslenzku sauðfé
BY
Stefan Adalsteinsson, Ph. D.
Abstract. This paper describes research on the inheritance of colours in the Icelandic
sheep and the relationshin hetween colour and fertility.
Three pigment types are found in the Icelandic sheep, i. e. tan, black and brown.
White sheep either lack pigment or show tan pigment. Nonwhite sheep show either
black or brown pigment, sometimes accompanied by tan pigment.
Four colour patterns are know in nonwhite sheep, grey, badgerface, mouflon and
grey mouflon. The patterns manifest themselves independently of whether the pigment
is black or brown.
Altogether 17 main colours are possible in Icelandic sheep, i. e. white and 16 different
nonwhite colours.
Broken colour in nonwhite sheep is expressed independently of pigment type and
pattern.
Colour genes are found at three loci, A, B and S. At the A-locus, 6 alleles are known:
Ai, A6, A2, A3, A4 and A5, giving the colours or patterns: White, grey mouflon, grey,
badgerface, mouflon and no pattern, respectively.
The dominance relationship among the above alleles is such that inhibition of pigment
production dominates over pigment production.
At the B-locus two alleles for pigment production are known, B4, dominant, giving
black pigment and B2, recessive, producing brown pigment.
Two alleles are known at the S-locus, S, dominant, giving unbroken colour, and
S2, recessive, giving broken colour.
No linkage has been found between the three loci above.
The A^-allele was shown to decrease fertility of ewes considerably, and some deviating
segregation results could be explained in terms of selective fertilization and selective
embryonic mortality.
The agreement between the present work and previous results reported in the litera-
ture is discussed and related to colour inheritance in rodents.
INTRODUCTION
Tlie aim of the study presented here is to
give an account of tlie inheritance of the
colours found in the Icelandic sheep and
the relation between colours and fertility.
1) Thesis presented for the Degree o£ Doctor
of Philosophy of the University of Edinburgh,
in the Faculty of Science.
The study of the inheritance of the
colours was initiated in 1957. At that time
the demand for grey skins from 4—5
months old lambs was increasing, and grey
skins of good quality fetched appreciately
higher prices than skins of other colours.
The initial aim of the study was there-
fore to work out the rules for the inherit-
ance of the grey colour. As the experi-