ABSTRACTS
265
flexed tail have been noted in these two animals.
Slight hydrocephalus with agnathis in Jersey calves
and hydrocephalus in crossbred dogs have also been
reported.
Two abnormal calves were born in a grade and pure-
bred Holstein-Friesian herd in the year of 1939-40.
The owner suspected his ration, although it was ade-
quate. Examination of the herd showed that the two
calves were from sire-daughter matings.
By special
arrangement 27 additional calves were produced in the
herd of such matings. Three peculiarities were noted
in these calves: viz. (1) a lethal, (2) asymmetrical
faces, and (3) a 'jumpy' nervous condition.
The lethal was manifest by an internal hydrocepha-
lus and marked papilloedema; the skull was enlarged
to two or three times its normal size.
There were
no apparent points of blockage of foramena, unless a
very abnormal position of the foramen magnum might
have partially or fully blocked the foramina of Magen-
dic and Luschka, 'thereby causing the hydrocephalus
as a secondary manifestation of a gene for bony abnor-
malities'. The humeri and femurs
were badly dis-
torted, giving rise to tremendous width of the hips
and crooked or twisted forelegs.
Asymmetry was
shown by a twisted appearance of the face caused not
only by the peculiar manner in which the face and
head were held, but also by irregularity in the length
of the two maxillae and of the two mandibles. In the
'jumpy' condition, muscular co-ordination was lacking,
the calf could not stand by itself unsupported, and
tremor was present whether standing or lying.
The three characters, it is suggested, are due to
three recessive autosomal genes.
The symbols given
are as follows : normal L. lethal l, symmetrical A,
asymmetrical a; and normal
nervous
reaction, J,
'jumpy' j. On this basis the sire was LlAaJj. Daugh-
ters of this bull and normal dams would have had
eight different genotypes, all normal, but nearly all
carriers of one or more of the three recessive genes
of the sire. The three abnormal characters would be
expected to appear in a definite proportion of the pro-
geny of these daughters
and their own sire. The
expected and observed distribution of phenotypes in
the 27 calves were sufficiently close to confirm
the
postulated mode of inheritance whether linked
or
unlinked, although the authors advise further study
of the mode of inheritance of 'jumpy' and asymmetry.
[J.N.W.]
Sex-linked albinism in the Turkey Meleagris
gallopavo. F. B. HUTT AND C. D. MUELLER.
J. Heredity 33, 69.
STUDIES of an albino poult and its relatives showed
that the condition is caused by a sex-linked recessive
gene which induces imperfect albinism.
A dingy white characterizes newly hatched affected
poults in which the irregular stripes and colour pattern
of Bronz poults are faintly visible. Mature birds had
some pigment in the feathers which was more evident
in the areas normally black.
Newly hatched poults
have a pale-grey iris which darkens with age.
The
pupil is red.
Histological examination of prepared
eye tissue showed absence of melanin in the pecten,
the pigment epithelium of the functional retina and
the choroid coat where it is normally abundant. Blind-
ness also characterized live affected poults.
In one pen of turkeys where this character
first
appeared there were 133 normal to 31 albinotic poults in
three hatches ; this ratio of practically 3:1 suggested a
simple recessive mutation.
If it were autosomal,
ratio of 101: 34 would have been expected from the
11 hens that produced albinos. The actual ratio was
106 :29. If the character were sex-linked the expected
ratio of normal to albinotic poults among-the 164 off-
spring from the one male would have been 123:41.
The observed ratio fits both expected ratios fairly well.
Eggs from a pen of turkeys among which the charac-
ter was observed were hatched. Three Bronz coloured
toms from these eggs were mated to normal hens and
two pens of normal coloured stock were made up from
the original pen. Dead embryos were examined if
24 days old.
All albinotic progeny from these mat-
ings were female in the ratio
of 184 coloured : 45
albinos. This again fits the expected ratio, showing
that the character is a sex-linked recessive mutation.
The symbol al is tentatively assigned to the character.
Of the 184 coloured poults from the five carrier
toms, 37 died at 24-28 days incubation: of the 45
albinos, 34 had died during this period. The fact
that the sex ratio of coloured embryos which died was
close to 1 female to 2 male, which is what would be
expected, showed that death in the albinos was due
to this character and not to the fact they were all
female.
Differential mortality prior to 24 days may
have accounted for the slight difference between the
observed and the expected ratios.
With very great difficulty one of the albinotic females
which was born alive was raised to maturity.
The
character reduces the viability of embryos and poults.
In the latter case blindness reduces the ability both to
find food and of defence. The gene al, therefore, can
be properly considered as a lethal gene. [J. N. W.].
The talpid lethal in the domestic fowl R. K
COLE (1942). J. Heredity 33, 83
Low hatchability may sometimes result from the pre-
sence of lethal genes which produce visible abnormali-
ties in the embryos. A system of recording the results
of examinations of dead embryos, including the age
at death, made it possible to recognize the talpid
lethal.
The name of this lethal was taken
from
talpa, the Latin for mole, because of the shape of
the embryotic appendages at death.
The lethal was first found in 1936 when a sire was
mated to his own daughters. The system of examin-
ing dead embryos revealed the character by the physi-
cal abnormalities resulting from it. Having found the
lethal it was learned that it had also appeared in 1935
as a result of matings of the same sire to some of his
own daughters. Dead embryos due to this gene, were
found also in 1937 in eggs from matings of birds dis-
tantly related to the sire mentioned. In the latter
year only 46.2 per cent of 26 fertile eggs from one hen
hatched, not entirely due to this lethal however,
whereas 100 per cent of 12 fertile eggs from a full
sister hatched.
The first common ancestor of all
carriers, pedigrees revealed, was a cock hatched in
1927.
The talpid embryos are characterised by reduced
length of proximal leg and wing bones, duplication of
the distal appendage bones, fused digits in the feet
and wings forming what appears like a webbed
hand, shortened vertebral column, extreme ectopia and
subcutaneous oedema, and a reduction of feather
papillae development. Death usually occurs on the 8th
to 10th day, although as late as the 17th day, of in¬
cubation. Birds heterozygous for the character show
none of the abnormalities.