Ricardo Cruz-Coke

Pure XX gonadal dysgenesis in identical twins

Pure gonadal dysgenesis has been described in several sibships. We report a pair of monozygous twins and their younger sister with secondary amenorrhea. They had no associated congenital anomalies. Plasma FSH levels were elevated and the ovarian biopsies showed absence of follicular structures. Their karyotypes were 46XX, further supporting the concept that this form of familial gonadal dysgenesis is an autosomal recessive defect.

Genetic Characteristics of Hemophilia A in Chile

A genetic and demographic study of 40 kindreds (113 cases) with hemophilia A, representing one quarter of all Chilean cases is reported. Only 10 sporadic cases were found. Segregation analysis of progeny from matings Aa X AY showed p = 0.2206 +/- 0.043. Fertility of 59 obligatory carriers was 3.88 children per mother with a mean age of 49.9 years, a figure higher than the mean of a control population, 3.36. The fertility of hemophiliacs was found to be 2.3 compared with their normal sibs with 3.15 children per couple. Life expectancy at birth in hemophiliacs was 22.4 years, compared with 28.1 for their normal brothers, 34.4 for their sisters and 58.5 and 64.6 for males and females in the general population. Mean relative fitness was calculated as 0.45 and the prevalence of hemophilia A in Chile as 1 case among 13,500 males. A preliminary estimate of the mutation rate was 1.35 X 10-5, within expected ranges. During the last 10 years, family planning and modern treatment with cryoprecipitates have increased the mean age of living hemophiliacs from 12.7 up to 22.7 years, and life expectancy from 15.6 to 22.4 years. Probably relaxation of natural selection will account for a possible increase of new cases of hemophilia A in the near future.

A general diagram of the human genome.

A general diagram of the whole structure of the human genome is drafted on a logarithmic metric scale located in the radius of a circle showing a full haploid set of chromosomes. A base pair scale of DNA is displayed in circumferences at different orders of magnitude from one metre down to one picometre (10(-12) m).

Nomogram for estimating specific consanguinity risks

This paper describes a nomogram to estimate the chance of consanguinity for specific autosomal recessive diseases, taking into account the gene frequencies (q) of the recessive alleles and the coefficient of inbreeding (F) of the family of the proband.

Complex familial translocation

Sirs, Schmidt & Passarge (1988) described a complex familial translocation involving three chromosomes; t(1;12)@22.l;q22) and dir ins (7;10)(ql1.2;q32.l;q42.1). In their Fig. 1, they showed paired chromosomes 1, 7 and 12 with five break rearrangements. It is difficult to understand this complex process simultaneously in their simple Fig. 1. In order to clarify this description, I am proposing to use a circular model of a chromosome map for reciprocal translocations (Cruz-Coke 1987). A circle array of the 24 chromosomes of the Human Genome has been presented independently by German (1987). Fig. 1 shows the reciprocal translocation of chromosomes 1 and 12 and the deletion of a segment of chromosome 1 and direct insertion of this segment in chromosome 7. The new formats of chromosomes 1, 7 and 12 are shown in the outer space of the circular model. Consequently, the complex process of five break rearrangements, translocations, deletions and insertions is simultaneously described in an overall picture of the whole genome. Ricardo Cruz-Coke

Pure XX Gonadal Dysgenesis in Identical Twins

Pure gonadal dysgenesis has been described in several sibships. We report a pair of monozygous twins and their younger sister with secondary amenorrhea. They had no associated congenital anomalies. Plasma FSH levels were elevated and the ovarian biopsies showed absence of follicular structures. Their karyotypes were 46XX, further supporting the concept that his form of familial gonadal dysgenesis is an autosomal recessive defect.