Chromosomes of cells grown in culture sometimes develop constrictions or gaps at particular locations called fragile sites ( FIGURE 9.19) because they are prone to breakage under certain conditions. A number of fragile sites have been identified on human chromosomes. One of the most intensively studied is a fragile site on the human X chromosome that is associated with mental retardation, the fragile-X syndrome. Exhibiting X-linked inheritance and arising with a frequency of about 1 in 1250 male births, fragile-X syndrome has been shown to result from an increase in the number of repeats of a CGG trinu-cleotide (see Chapter 19). However, other common fragile sites do not consist of trinucleotide repeats, and their nature is still incompletely understood.
www.whfreeman.com/pierce For gorilla and other great-ape chromosomes with a comparison of the human karyotype
I 9.19 Fragile sites are chromosomal regions susceptible breakage under certain conditions.
(Erica Woollatt, Women's and Children's Hospital, Adelaide).
The New Genetics ethics science •technology Fragile X Syndrome
Ryan, age 4, is brought to the medical genetics clinic by his 27-year-old mother, Janet. Ryan is developmentally delayed and hyperactive and has undergone many tests, but all the results were normal. Janet and her husband, Terry, very much want another child. The family history is unremarkable with the exception of the 6-year-old son of one of Janet's cousins, who is apparently "slow." However, Janet reports that she does not get along with her siblings and that in fact she has little contact with any of the rest of her family. Both her parents are deceased. A friend told her recently that Janet's 25-year-old sister just found out that she is pregnant with her first child.
The cause of Ryan's delay is determined to be Fragile X-syndrome. As its name suggests, this condition is a sex-linked disorder carried by females and most seriously affecting males, in whom it can cause severe mental retardation. After describing the genetics of Fragile X-syndrome and its hereditary risks, the medical geneticist asks Janet to notify her sister of the information and alert her to the availability of prenatal testing. The next week, the geneticist calls Janet, who states that she has not called her sister and does not intend to.
Are there ways that the geneticist can persuade Janet to inform her sister? Failing that, can the physician alert Janet's sister to her risk without compromising the obligation to preserve the confidentiality of the relationship with Janet? If there is no other recourse, does the genetic professional have an ethical or legal right to breach confidentiality and inform Janet's sister—and perhaps others in the family—of the risk? Does the professional have a duty to do so? By law, a professional's ethical duty to a patient or client can be overridden only if (1) reasonable efforts to gain consent to disclosure have failed; (2) there is a high probability of harm if information is withheld, and the information will be used to avert harm; (3) the harm that persons would suffer is serious; and (4) precautions are taken to ensure that only the genetic information needed for diagnosis or treatment or both is disclosed. However, who determines which genetic risks are among the "serious harms" that would permit breaching confidentiality in medical contexts?
Some might argue that all these questions miss the point: the familiar duties of doctor and patient don't apply in this case because, where genes are concerned, the patient is not the individual, but the entire family to which that patient belongs. Thus, the physician must do whatever best meets the needs of all members of the family. This line of reasoning may be increasingly popular as the powers of genetic medicine grow and physicians are more frequently asked to utilize and interpret genetic tests in the course of routine care. Nevertheless, we should be careful not to hastily discard the traditional ethical principle that the doctor's and medical team's first responsibility is to the presenting patient. Replacing it with a generalized responsibility to the whole family takes medical practice into uncharted territory and can impose serious new burdens on medical professionals.
In this case, the patient refuses to inform other family members who might benefit from prenatal testing— which would allow them to decide to continue or terminate a pregnancy or prepare for the birth of a child with a genetic disorder. But the same type of problem can arise in many other ways where genetic medicine or research is concerned. In some conditions, testing is aimed at determining whether an individual or family has a genetic
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