Mexican geneticists' views of ethical issues in genetics testing and screening. Are eugenic principles involved?

Herein we discuss Mexican geneticists' views of ethical issues in genetic testing and screening, analyzing whether eugenic principles are involved in this activity. The information was obtained from a comprehensive survey on genetics, ethics, and society organized by Wertz and Fletcher in 1993, in which 37 nations participated. The responses to 21 questions from 64 out of 89 (72%) geneticists invited to participate are analyzed in this paper. The questions were practically the same as those answered recently by a group of Chinese geneticists (Mao X. Chinese geneticists' views of ethical issues in genetic testing and screening: evidence for eugenics in China. Am J Hum Genet 1998: 63: 688-695), who work in a country where the furtherance of eugenic principles is considered to be the goal of human genetics. We concluded that although there are many similarities in the answers from both countries, this is not indicative of Mexican geneticists pursuing eugenic goals because: a) there is no coercion involved; and b) there is no intention of improving the gene pool.

Mexican geneticists' opinions on disclosure issues.

Here we discuss the opinion on disclosure issues (respect for confidentiality) of Mexican professionals working in clinical genetics. The information was obtained from a comprehensive survey on genetics, ethics and society organized by Wertz and Fletcher in 1993, in which geneticists from 37 nations participated. The responses to 18 questions from 64 of 89 (72%) geneticists invited to participate were analyzed for this paper. The questions were directed to investigate: a) disclosure of clinically relevant information in several situations such as testicular feminization syndrome, mosaic de novo balanced translocation in a fetus, or accidental discovery of non-paternity; b) the protection of patient's privacy from the spouse or blood relatives; and c) confidentiality in cases with high genetic risk to relatives. The results reveal significant disparity between general responses related to disclosure of all clinically relevant information and specific responses in particular cases. In addition, professionals appear to give higher priority to protecting the spouse, blood relatives or public safety, rather than the patient's confidentiality.

Attitudes of Mexican geneticists towards prenatal diagnosis and selective abortion.

Prenatal diagnosis (PD) provides the physician information on whether the unborn fetus has a genetic or chromosomal disorder, and offers patients a new option: selective abortion. In the present study, we analyzed the answers Mexican geneticists provided to a few selected questions from a multinational survey designed by Wertz and Fletcher [1988: Am J Hum Genet 42:592-600]. The selected questions were related to the use of PD, the acceptance of selective abortion, and the self-reported directiveness of counselling following the diagnosis of a fetal anomaly. Our results show that the great majority of Mexican geneticists participating in the study agree with PD when medically indicated, but not on free demand. Specific cases stimulated the group on thinking more than the general statements provided in the survey. Although the majority agreed that PD should be available to all women, when faced with cases of nonmorbid maternal anxiety, paternity testing, and sex selection, the proportion of geneticists willing to perform the test decreased substantially. When counselling patients on a fetal anomaly, the minority would be as unbiased as possible, and this seems to be the tendency in developing countries where counselling, as stated in the respondents' comments, reflects the belief that the goal of genetics is the prevention of or opposition to abortion. Counselling was influenced by the severity of the disorder. The geneticists' personal attitude toward abortion in the same situations was stronger than when counselling others. Analysis of directiveness in counselling for fetal anomaly showed that older geneticists, with more years of experience in medical genetics, were more likely to be neutral. When counselling directively, the group showed an overall direction toward continuing affected pregnancies. However, older geneticists and those with more than 10 years of practice were more likely than their younger counterparts to counsel towards terminating affected pregnancies. In personal situations of fetal disorder, the general tendency was to abort; however, geneticists seeing more than 5 patients per week, and those who believe that religion is important, were more likely to reject abortion. The sample is representative of Mexican geneticists, and the main limitation of this study is that the geneticists have very little experience in PD, and that their responses were mostly based on theory. However, their opinions may influence the demand and the availability of PD and abortion, as well as the possibility of legalization of abortion on the basis of a fetal defect.

[Genetic influence on energy requirements. III. Multifactorial inheritance modified by gender]. / Influencia genética en requerimientos de energía. III. Herencia multifactorial modulada por género.

A conversion index (CI) which measures the efficiency of utilization of dietary energy was found to be normally distributed in Wistar rats. The CI used was a ratio of the amount of food ingested to achieve an increment of one gram of body weight during the period of 32 days starting on day 21 after weaning. We have previously reported that male rats are more efficient energy converters than females. As a way to explore the hypothesis that the inheritance of the regulation of energy requirements is multifactorial, we mated F1 rats with high CI (poor energy converters) and studied the CI of their F2 offspring. The males behaved in agreement with the hypothesis as the F2 males had higher CI than the F1 males, but the behavior in females was different, i.e. the F2 were better converters than the F1. We have no explanation for this gender discrepancy.

Utilization of dietary energy in the rat. IV. Multifactorial inheritance modulated by gender.

In Wistar rats the conversion indexes (CIs) are normally distributed. A conversion index is the amount of food consumed necessary to increase the body weight by 1 g in a 32-day period, which begins at weaning (day 21) and ends on the 52nd day of life of the rat. Some experiments have been designed trying to demonstrate that inheritance of energy dietary utilization in Wistar rats may be multifactorial modulated by gender. In the study presented here parental males (F1) with CIs below the male median were paired with females of the same F1 who also had CIs below the female median. It was postulated, if the hypothesis is correct, that the offspring (F2) obtained from these pairings would have conversion indexes below the median of the CIs of the parental rats(F1). The results indicate precisely that both males and females behave as expected. Thus it appears that inheritance of efficiency of dietary energy utilization in the Wistar rat is a multifactorial trait.

[Polymorphisms of chromosomes 1, 9, and 16 in Mexican mestizos]. / Polimorfismos de los cromosomas 1, 9 y 16 en mestizos mexicanos.

The frequency of heterochromatic polymorphisms on C-banded chromosomes 1, 9 and 16 in two inter-racial Mexican populations was analyzed. Secondary constriction (qh) regions were classified according to a semi-quantitative procedure which showed to be simple and convenient. We compare our results with those in other populations.

[Genetic influence on energy requirements. I. Development of an experimental model]. / Influencia genética sobre los requerimientos de energia. I. Desarrollo de un modelo experimental.

In attempting to explore the mechanisms of interaction of genetic and environmental factors that affect the quantitative requirements of energy by man, the convenience of an animal model was considered and searched for. The idea was to start with male and female Wistar rats and through inbreeding segregate the highly effective users of energy from the poor users. The efficiency of dietary energy utilization was measured by the index of conversion (IC) defined as the dietary intake necessary to increase 1 g of body weight in a 32-day period, from day 21st to day 52nd of extrauterine life. The median value of the IC for all animals included in each experiment was the cut-off point to classify each individual as a good or a poor energy user. The first generation had three males and five females with a median IC = 2.90 and a range from 2.54 to 3.25. The proportion of males below the median was 3/3 while the proportion of females was 2/5. The difference in proportions was striking and led immediately to the consideration of a sex-link hypothesis, and to test it the, IC of 91 Wistar rats randomly selected at birth was obtained. The median value of the series was 2.99 with a range from 2.24 to 3.95. The proportion of male rats with values below the median was 33/38 while the corresponding proportion for females rats was 13/53. In other words, while nine of every ten male animals were good users of energy, only two out of ten females fell into this category.(ABSTRACT TRUNCATED AT 250 WORDS)

[Cytogenetic study of the parents of 85 index cases with regular trisomy 21]. / Estudio citogenético en los progenitores de 85 casos índice con trisomía 21 regular.

The parents of 85 Down syndrome cases with regular 21 trisomy were studied cytogenetically. The lymphocyte chromosomes were stained with G-banding technique and 100 metaphases were analyzed in the father, the mother and the index case. Among the mothers two cases of mosaic 46, XX/47, XX, +21 (2.35%) were found and among the fathers no mosaic cases were found. Reciprocal and robertsonian translocations were not observed. In one of the fathers a pericentric inversion of the Y chromosome (0.61%) was found. The results are compared with those of similar studies and discussed in relation to genetic counseling and to the possible existence of an "interchromosomal effect" in man.

Utilidad de los heteromorfismos cromosómicos obtenidos por bandas G para la identificación de ilegitimidad / Usefulness of G chromosome banding for illegitimacy detection

Se investigó la utilidad de algunos heteromorfismos cromosómicos obtenidos por bandas G para identificar hijos ilegítimos. En 80 familias se estudiaron a ambos padres y a 171 de sus hijos, estableciéndose además la sensibilidad de los marcadores. Los resultados mostraron que de los 171 hijos uno (0.6//) era ilegítimo, cifra muy inferior a la obtenida con el uso de varios grupos sanguíneos y marcadores séricos que fue de 6.7 por ciento en un grupo similar de familias. Se pudo demostrar que el bajo índice de detección de ilegitimidad de los heteromorfismos cromosómicos se explica, parcialmente cuando menos, por la baja sensibilidad de los mismos la cual fue de 27 por ciento en comparación con una sensibilidad de 60 por ciento encontrada con los otros marcadores genéticos

[Usefulness of chromosomal heteromorphisms obtained by G-banding for identification of illegitimacy]. / Utilidad de los heteromorfismos cromosómicos obtenidos por bandas G para la identificación de ilegitimidad.

The present paper investigates the use of G-bands chromosome heteromorphisms for illegitimacy testing. We studied both parents and 171 of their children in 80 families utilizing the material, in addition, to establish the procedures sensitivity. The results showed that one (0.6%) of the 171 children studied was illegitimate, which was much lower than the figure of 6.7% obtained in a similar population studied with three blood group systems and three serum genetic markers. We could show that the low efficiency of the G-band heteromorphisms is at least partially due to its low sensitivity, 27% as compared to 60% obtained with the other genetic markers.

[Frequency of mixoploidy in 85 index cases with Down syndrome]. / Frecuencia de mixoploidías en 85 casos índice con síndrome de Down.

A lymphocyte chromosome analysis was done in 85 cases of trisomy 21 Down syndrome, the objective being the identification of the frequency of mosaicism. In each case an attempt was made to analyse at least 100 metaphases. Sixteen cases of mixoploidy were found (18.8%) with two or more cellular lines. These findings are discussed in relation with the frequency of the association between Down's syndrome and other aneuploidies, the frequency of the diploid/trisomy 21 mosaicism, and the possible origin of the latter.