Robert N. Shoffner

XY sex-reversal syndrome in the domestic horse

The XY sex-reversal syndrome occurs when a phenotypic mare is born that has the karyotype of a stallion. The syndrome is manifested by both genotypic and phenotypic heterogeneity. The sex-reversed genetic condition occurs frequently within certain pedigrees where XY females have been found and can be readily detected by chromosome karyotyping. The phenotypic spectrum ranges from the feminine mare with a reproductive tract that is within normal limits to the greatly masculinized mare. Pedigree analysis suggests that there are two modes of inheritance: (1) an X-linked recessive or autosomal sex-limited dominant transmitted through the female and (2) an autosomal sex-limited dominant or a Y chromosomal mutation with variable expression transmitted through the male. The proportion of female to male progeny of the 69 top-producing Arabian stallions in the world is 53 to 47, indicating that the occurrence of genetic defects affecting the sex ratio such as the XY sex-reversal syndrome is relatively infrequent. In nine cases where the sex ratios of stallions deviated significantly from the expected sex ratio, the incidence of female infertility also increased. Cytogenetic screening of young animals would provide for early detection and avoid the expense and disappointment of continuous breeding attempts. Just as importantly, it would aid in the reduction and the possible elimination of this genetic condition from breeding herds.

Coturnix coturnix japonica

The materials for the karyograms were prepared from feather pulp and embryonic tissue of coturnix quail secured through the courtesy of Dr. Hans Abplanalp, University of California, Davis. This colony originated from Japan. This species is one of the few among the birds so far described that have metacentric or submetacentric chromosomes recognizable to about chromosome size twenty.

Trypsin G- and C-banding for interchange analysis and sex identification in the chicken

The trypsin banding methods were applied to feather pulp and embryonic material of the chicken. Two contrasting types of chromosomal banding patterns were obtained by varying the duration of trypsin treatment. A short time treatment shows a G-banding pattern which has characteristic and distinctive bands along the chromosome arms. Prolonging the trypsin treatment causes the G-banding pattern to disappear, and only the centromeres and the W chromosome remained heterochromatic which is characteristic of the C-banding pattern. The application of the G-banding pattern analysis was used to identify regions of chromosomes involved in rearrangements. The simplified trypsin technique which produces the C-banding pattern makes it relatively easy to identify the W sex-chromosome and determine sex in avian species.

Mate preference in wild and domesticated (game-farm) mallards: II. Pairing success

Abstract Experiments were designed to determine whether assortative mating occurs in wild and game-farm mallard strains (Anas platyrhynchos). Mallard males of either strain raised with females of their own strain courted females of their own strain more than females of the opposite strain, and these males were only successful in pairing with females of their own strain. Males raised with females of the opposite strain courted wild and game-farm females with equal intensity. They were successful in pairing with females of either strain. While this study does not settle the question of possible gene flow between these two mallard populations, it does indicate that there is a potential barrier to panmixia.

Mate preference in wild and domesticated (game-farm) mallards (Anas platyrhynchos): I. Initial preference

Abstract Wild and game-farm mallards (Anas platyrhynchos) raised in pure strain and mixed groups were tested for initial mate preference in a choice test. Female mallards showed no significant preference but males of either strain raised with females of their own strain significantly preferred female models of their own strain during the test. Males raised with females of the other strain merely showed attenuation of their preference for female models of their own strain and did not show preference for female models of the other strain. Game-farm mallards approached models significantly sooner than wild mallards and there was a significant sex × mate interaction.

XY sex reversal syndrome in the mare: clinical and behavioral studies, H-Y phenotype.

SummaryAn inherited genetic disorder causes XY embryos of the horse to develop as mares. On the basis of our study of 38 such mares, we have identified four grades or classes of XY sex reversal according to this scheme: class I, nearly normal female, of which some are fertile; class II, female with gonadal dysgenesis, normal mullerian development; calss III, intersex mare with gonadal dysgenesis, abnormal mullerian development, enlarged clitoris; class IV, virilized intersex characterized by high levels of testosterone. In general, class I and calss II mares were typed H-Y antigen-negative whereas class III and class IV mares were typed H-Y antigen-positive.

Mitotic chromosomes and the W-sex chromosome of the great horned owl (Bubo V. virginianus).

SummaryMitotic chromosomes from the feather pulp and leucocyte cultures of the great horned owl (Bubo v. virginianus) were analyzed in both the sexes. The largest pair of chromosomes are acrocentrics while those of the second and the third pair have a short arm 1/6th the size of the large one. Chromosomes of the fourth and the fifth pairs have a median constriction while those of the 6th to 9th pairs are all acrocentrics. These are followed in order of size by a large number of smaller chromosomes, the smallest of which appear as dots. In 15 plates out of a total of 21, 82 to 84 chromosomes were counted and it is presumed that either of these numbers represents the diploid number. In the female sex besides the single unpaired 4th Z-chromosome, there is a small metacentric unpaired “W” chromosome which is nearly equal in size to the chromosomes of the 7th pair.

Xenopus laevis Daudin

The pair of large acrocentric autosomes bears a secondary constriction and satellites on the short arm.

MATING BEHAVIOUR AND FERTILITY IN DOMESTIC CHICKENS. I. INBREEDING

Abstract Mating behaviour of males and females of the Inbred line 420 Single Comb White Leghorn chickens was compared with that of the random-bred Minnesota Marker line in a factorial experiment with two replications. Inbred males showed less frequency of approaching females, waltzing, treading and tail-bending, but did not differ from random-bred males in frequency of attempted and successful mountings. Inbred females showed fewer crouchings and completed fewer matings than random-bred females. Fertility was associated with the interaction of male and female behaviour.

Induction of heteroploidy in Gallus domesticus

Intraperitoneal colcemid injection at the dose level of 0.37 mg/kg applied 3-4 h before the first oviposition produces a high frequency of triploids among the second oviposition eggs laid the first day after colcemid treatment. The triploids, mostly 3A-ZZW type, appear to be as developmentally compatible as contemporary diploids at both embryonic and hatching level. No other kinds of heteroploids besides triploids were found at hatching time even though a high frequency was observed in 24-h embryos.