The advent of the "unpatients'.

Predictive diagnosis by molecular methods will change the scientific basis of prognostics. At the same time, it will change the ethical dimensions of the relation among patients, their doctors and other providers of care.

Concerted evolution of primate alpha satellite DNA. Evidence for an ancestral sequence shared by gorilla and human X chromosome alpha satellite.

To understand evolutionary events in the formation of higher-order repeat units in alpha satellite DNA, we have examined gorilla sequences homologous to human X chromosome alpha satellite. In humans, alpha satellite on the X chromosome is organized as a tandemly repeated, 2.0 x 10(3) base-pairs (bp) higher-order repeat unit, operationally defined by the restriction enzyme BamHI. Each higher-order repeat unit is composed of 12 tandem approximately 171 base-pair monomer units that have been classified into five distinct sequence homology groups. BamHI-digested gorilla genomic DNA hybridized with the cloned human 2 x 10(3) bp X alpha satellite repeat reveals three bands of sizes approximately 3.2 x 10(3), 2.7 x 10(3) and 2 x 10(3) bp. Multiple copies of all three repeat lengths have been isolated and mapped to the centromeric region of the gorilla X chromosome by fluorescence in situ hybridization. Long-range restriction mapping using pulsed-field gel electrophoresis shows that the 2.7 x 10(3) and 3.2 x 10(3) bp repeat arrays exist as separate but likely neighboring arrays on the gorilla X, each ranging in size from approximately 200 x 10(3) to 500 x 10(3) bp, considerably smaller than the approximately 2000 x 10(3) to 4000 x 10(3) bp array found on human X chromosomes. Nucleotide sequence analysis has revealed that monomers within all three gorilla repeat units can be classified into the same five sequence homology groups as monomers located within the higher-order repeat unit on the human X chromosome, suggesting that the formation of the five distinct monomer types predates the divergence of the lineages of contemporary humans and gorillas. The order of 12 monomers within the 2 x 10(3) and 2.7 x 10(3) bp repeat units from the gorilla X chromosome is identical with that of the 2 x 10(3) bp repeat unit from the human X chromosome, suggesting an ancestral linear arrangement and supporting hypotheses about events largely restricted to single chromosome types in the formation of alpha satellite higher-order repeat units.

Attitudes and interest in genetic testing for breast and ovarian cancer susceptibility in diverse groups of women in western Washington.

OBJECTIVES: This paper examines the knowledge, opinions, and predictors of interest in genetic testing for breast cancer risk in a demographically diverse group of women in western Washington who participated in a randomized controlled trial (RCT) of breast cancer risk counseling methods. MATERIALS AND METHODS: Four groups of women were surveyed, all with some family history of breast cancer: (a) 307 white women; (b) 36 African-American women; (c) 87 lesbian/bisexual women; and (d) 113 Ashkenazi Jewish women. As part of the baseline questionnaire for the RCT, participants were asked about their familiarity with genetic testing for breast cancer risk, their interest in such testing and opinions of it, and actions they anticipated based on test results. RESULTS: Women in all four groups favored ready access to testing, believed the decision to be tested should be a personal choice, believed that genetic test results should stay confidential, and were not greatly concerned that this might not be possible. Women anticipated using such genetic test results to increase the frequency of various breast cancer screening methods (in all four groups, > 69% would increase mammogram frequency, > 85% would increase clinician exam, and > 92% would increase breast self exam). Women overwhelmingly rejected prophylactic surgery as a preventive measure (in all > 80% probably or definitely would not consider it). Significant predictors of interest in genetic testing for cancer risk included perceived risk, cancer worry, and beliefs about access to testing. CONCLUSIONS: These data will be of interest to health care providers, payers, public health professionals, legislators, and others as they consider issues associated with population testing for susceptibility to common diseases such as breast cancer.

Testing for inherited susceptibility to breast cancer: a survey of informed consent forms for BRCA1 and BRCA2 mutation testing.

The identification of genetic mutations linked to breast cancer has made it possible to test for the genetic predisposition to this disease. However, though this test may provide certain benefits, there are also potential risks involved with the testing process, including social and economic considerations. In light of these potential risks, we sought to determine what information individuals are receiving in the informed decision making process. To learn the minimal amount of information the actual testees receive, we obtained 10 informed consent forms from seven different testing facilities. These testing centers include the major sources of BRCA1 and BRCA2 mutation testing in the United States at this time. We analyzed the content of these forms by developing content categories and scoring them appropriately. We found all ten forms discussed in varying ways and to varying degrees the purpose of genetic testing, limitations of the test, implications of both positive and negative results, and confidentiality procedures; most, but not all, addressed various psychological and insurance risks. Overall, the forms demonstrated substantial variation in content and organization, underlining the need for more discussion and research on the purpose, nature, and effectiveness of informed consent forms for this type of genetic test.

Women's interest in genetic testing for breast cancer susceptibility may be based on unrealistic expectations.

We report on results of an interview study assessing women's attitudes toward and hypothetical interest in genetic susceptibility testing for breast cancer. Data are from 246 interviews with women of varying ethnicity (African American, European American, Native American, and Ashkenazi Jewish), family history of breast cancer (negative, positive, and borderline), and educational level. Semistructured interviews included questions on general health beliefs; attitudes, experiences, and concerns about breast cancer; and hypothetical interest in genetic testing. Influence of specific test characteristics was assessed with 14 Likert scales varying negative and positive predictive value, timing of disease, possible medical interventions following a positive result. Results reported include both statistical and qualitative analysis. We found that women had a high level of interest in testing which, in general, did not vary by ethnicity, level of education, or family history. Interest in testing appeared to be shaped by an exaggerated sense of vulnerability to breast cancer, limited knowledge about genetic susceptibility testing, and generally positive views about information provided through medical screening. However, study participants were most interested in a test that didn't exist (high positive predictive value followed by effective, noninvasive, preventive therapy) and least interested in the test that does exist (less than certain positive predictive value, low negative predictive value, and limited, invasive, and objectionable therapeutic options). Our data suggest that without a careful counseling process, women could easily be motivated toward interest in a test which will not lead to the disease prevention they are seeking.

Ethics and the Human Genome Project.

This article provides an overview of ethical issues in genetic testing and screening as they are currently considered in relationship to the Human Genome Project. Previous landmark reports and policy recommendations on genetic testing and screening are briefly described. The goals and research interests of the joint National Institutes of Health/Department of Energy Ethical, Legal, and Social Working Group of the Human Genome Project are outlined. To provide an example of one method by which ethical issues in genetics may be addressed, the ethical framework and practical aspects of a clinical ethics research project at the University of Washington, Seattle, are described. Finally, future directions for the study of ethical and social issues related to genetic testing and screening programs are suggested.

Molecular analysis of a polymorphic domain of alpha satellite from the human X chromosome.

Alpha satellite DNA, a diverse family of tandemly repeated DNA sequences located at the centromeric region of each human chromosome, is organized in a highly chromosome-specific manner and is characterized by a high frequency of restriction-fragment-length polymorphism. To examine events underlying the formation and spread of these polymorphisms within a tandem array, we have cloned and sequenced a representative copy of a polymorphic array from the X chromosome and compared this polymorphic copy with the predominant higher-order repeat form of X-linked alpha satellite. Sequence data indicate that the polymorphism arose by a single base mutation that created a new restriction site (for HindIII) in the sequence of the predominant repeat unit. This variant repeat unit, marked by the new HindIII site, was subsequently amplified in copy number to create a polymorphic domain consisting of approximately 500 copies of the variant repeat unit within the X-linked array of alpha satellite. We propose that a series of intrachromosomal recombination events between misaligned tandem arrays, involving multiple rounds of either unequal crossing-over or sequence conversion, facilitated the spread and fixation of this variant HindIII repeat unit.

Patterns of intra- and interarray sequence variation in alpha satellite from the human X chromosome: evidence for short-range homogenization of tandemly repeated DNA sequences.

A number of processes, such as sequence conversion, unequal crossingover, and molecular drive, have been postulated to explain the homogenization of tandemly repeated DNA families. To investigate the nature and extent of such processes in the alpha satellite family of centromeric DNA, we determined the nucleotide sequence of approximately 700 bp from each of 40 representative alpha satellite repeats from six sources of human X chromosomes, obtaining a total of approximately 28 kb of sequence data. Sequence divergence among the repeats examined was low, with an average pairwise difference of approximately 1%. Pairwise comparisons of all repeats indicate that the degree of similarity for those repeats in physical proximity (within approximately 15 kb) of each other is significantly greater than that for randomly located repeats, from either the same or different X chromosomes, suggesting that the mechanisms predicted to homogenize these arrays are effectively short-range in action. Analysis of individual patterns of sequence variation allows the assignment of haplotypes for five high-copy-number diagnostic positions and reveals distinct positions of equilibrium and disequilibrium within the repeat. These analyses address hypotheses about the origin of the observed patterns of variation throughout alpha satellite evolution.

Chromosome-specific alpha satellite DNA from human chromosome 1: hierarchical structure and genomic organization of a polymorphic domain spanning several hundred kilobase pairs of centromeric DNA.

The human alpha satellite repetitive DNA family is organized as distinct chromosome-specific subsets localized to the centromeric region of each chromosome. Here, we report he isolation and characterization of cloned repeat units which define a hierarchical subset of alpha satellite on human chromosome 1. This subset is characterized by a 1.9-kb higher-order repeat unit which consists of 11 tandem approximately 171-bp alpha satellite monomer repeat units. The higher-order repeat unit is itself tandemly repeated, present in at least 100 copies at the centromeric region of chromosome 1. Using pulsed-field gel electrophoresis we estimate the total array length of these tandem sequences at the centromere of chromosome 1 to be several hundred kilobase pairs. Under conditions of high stringency, the higher-order repeat probe hybridizes specifically to chromosome 1 and can be used to detect several associated restriction fragment length DNA polymorphisms. As such, this probe may be useful for molecular and genetic analyses of the centromeric region of human chromosome 1.

Regional localization of the TIMP gene on the human X chromosome. Extension of a conserved synteny and linkage group on proximal Xp.

The gene encoding a tissue inhibitor of metallo-proteinases, TIMP, has previously been shown to be X-linked in both the human and mouse genomes. We have used a series of somatic cell hybrids segregating translocation and deletion X chromosomes to map the TIMP gene on the human X chromosome. In combination with previous data, the gene can be assigned to Xp11.23----Xp11.4. Genetic linkage analyses demonstrate that TIMP is linked to the more distal ornithine transcarbamylase (OTC) locus at a distance of about 22 centimorgans. The data are consistent with the conclusion that TIMP maps to a conserved synteny and linkage group on the proximal short arm of the human X chromosome and on the pericentric region of the mouse X chromosome, including loci for synapsin-1, a member of the raf oncogene family, OTC, and TIMP.