The preferential location of the human Y chromosome in somatic metaphase. I. Influence of Y polymorphism.

The location of the Y chromosome in metaphase figures was studied, with respect to its polymorphism, on 700 micrographs from blood lymphocyte cultures from 70 normal male members of seven Canadian family lines whose polymorphic Y chromosomes were inherited in a patrilinear fashion from seventeenth-century French ancestors. Three of these family lines were carriers of a long Y chromosome, two a small one, one had an average length Y and a seventh one had a satellited Y marker. The Y chromosome was peripheral in 75 to 90 per cent of the metaphase plates from each individual investigated. The long Y markers were more peripheral than the small ones while the average length Y chromosome had an intermediate position, whereas the satellited Y chromosome was located within the small group. The difference between the location of the long and the small Y chromosomes was highly significant. It is hypothesised that a heteromorphic Y might affect the nonrandom orientation of metaphasic chromosomes and favour meiotic nondisjunction and aneuploidy.

The influence of the length of the human Y chromosome on spontaneous abortions. A prospective study in family lines with inherited polymorphic Y chromosomes.

Following reports indicating a close association between the presence of a long Y chromosome in males and the risk of spontaneous abortion in their female partners, the incidence of spontaneous fetal loss was investigated in four family lines whose patrilineary ancestors emigrated from France to Canada during the second half of the seventeenth century. In two of the lines the males were carriers of a Yq+, in the other two the males had a Yq- or a normal Y chromosome. Results showed that in one of family lines with a Yq+, 17/26 (65.4%) wives had 33 (2.8%) spontaneous abortions in 151 pregnancies, whereas in each of the three other family lines 7/30 (23.3%) wives aborted 8 (4.9%), 15 (7.5%) and 10 (5.7%) times in 165, 200 and 175 pregnancies respectively. The high incidence of fetal loss found in one of the family lines whose males have a long Y chromosome correlates with previous observations on the influence of Yq+ on spontaneous abortions, and draws attention to the inheritable nature of this peculiarity. However, the low incidence of miscarriages observed in the other family line carrying a Yq+ seems to indicate that long Y chromosomes are of various types and could be produced by several mechanisms. Yq- does not seem to represent an increased risk of pregnancy loss. Results also demonstrated that while a long Y chromosome may affect the viability of the zygote, it does not affect the fertility of its carrier.

[Unusual chromosomal rearrangement. An autosomal telomeric translocation on a multicentury satellited Y (Yqs) chromosome]. / Un remaniement chromosomique inhabituel. Une translocation télomérique autosomique sur un Y à satellites (Yqs) multicentenaire.

A new born male infant with craniostenosis and minor phenotypic malformations was found to have a satellited Yq chromosome with, translocated on its satellite, a segment from the terminal part of the long arm of a presumed autosome 14. The rearrangement is de novo since the propositus' father has a non-rearranged satellited Y chromosome and he is, furthermore, a member of a family line in which a Yqs is transmitted in patrilineary fashion since 1668. Such and autosomal translocation on a satellited Y chromosome is a very rare event, because the abnormality makes up a double rearrangement on the same arm of a chromosome, with a three-century interval between the two phenomenons. A presumed partial trisomy 14q is associated with the clinical picture of the case.

[Absence of the palmar c triradius. Dermatoglyphic and geneologic study of a genetic character transmitted since the 17th century in a Quebec family]. / L'absence du triradius C palmaire. Etude dermatoglyphique et généalogique d'un caractère génétique, transmis depuis le dix-septième siècle, dans une lignée familiale québécoise.

A dermatoglyphic research on the absence of the palmar c-triradius was carried out in a Canadian family line originating from a French married couple who settled in the Quebec City area in 1649. Of the 51 individuals examined, 34 showed that c-triradius was missing on one or both palms. The study of the family tree and of the data confirms the hypothesis that an absent palmar c-triradius is an autosomal dominant trait transmitted by an heterozygous genotype with, in the present observation, an incidence of 66,6% and an estimated penetrance of 44,1%.

The chromosomes of the Canadian Beaver Castor canadensis.

A chromosome analysis of 24 Canadian beavers, Castor canadensis Kuhl (12 males and 12 females), captured in Laurentides Park, Qébec, has been performed from preparations of blood lymphocyte and skin cultures. The chromosome number was found to be 2n = 40. Measurements were made to determine relative lengths and arm ratios of chromosomes, which are metacentric or submetacentric. Results are in agreement with those already published regarding the chromosome number, but differ in the identification of the X chromosome, and in the morphology of the Y and some autosomes. C- ad G-banding techniques allowed the precise identification of individual chromosome pairs. A detailed idiogram of G-bands is presented.