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4 Health L.J. 119 (1996)
Genetic Screening and Testing in Canada: A Model Duty of Care

handle is hein.journals/hthlj4 and id is 125 raw text is: Genetic Screening and Testing in Canada: A Model Duty of Care Neil F. Sharpe* I Introduction New and emerging diagnostic and prognostic genetic tests' will soon provide the ability to predict the likelihood of individuals having or transmitting a specific genetic disease.2 Prenatal screening for sickle cell anemia, Tay-Sachs disease and Neil F. Sharpe, B.A., LL.B., LL.M., Human Genome Consulting Group, Hamilton, Ontario, Canada. For a general review of the role of genetics in medicine, see: Science Council of Canada. Genetics in Canadian Health Care (Ottawa: Minister of Supplies and Services, 1991) at 1, 19- 27, and 57. In the U.S., it is estimated that in the near future, each year 2.7 million genetic tests will be conducted for cystic fibrosis, sickle cell anemia, hemophilia, or Duchenne muscular dystrophy, 2.4 million tests to detect chromosome abnormalities, and 16.2 million tests for common diseases including breast cancer and Alzheimer disease. Also, M.W. Thompson, R.R. Mclnnes & H.F. Willard, Genetics in Medicine, 5th ed. (Philadelphia: W.B. Saunders 1991) at 1-11. Teresa Costa et al., The Effect of Mendelian Disease on Human Health: A Measurement (1985) 21 Am. J. Med. Genet. 231 at 232. This paper will utilize the definition of genetic disease defined in the Costa study as a disorder for which a variant DNA sequence is a major determinant and whose manifestations result in impairment, disability, and handicap with some disadaptive consequences for the individual It is necessary to distinguish between simple genetic diseases, and more complex genetic diseases which run in families but whose origins are neither single-gene nor chromosomal. Single-gene defects segregate within families. Classifications include the autosomal dominant gene - such as the Huntington disease gene - that always will be expressed, although the age of the disease's on-set and the degree of severity of disease expression can vary considerably; and the autosomal recessive gene - such as the Cystic fibrosis gene - which is expressed only if an individual has inherited two paired recessive genes (one from each parent). To illustrate the patterns of human gene inheritance, when two quarters are flipped, there are four possible results: A) both coins showing heads; B) both coins showing tails; C) the first coin showing heads, the second tails; D) the first coin showing tails, the second heads. If one parent has one autosomal dominant gene and one normal gene, and the other parent has two normal genes, the first child generally will have a 50% risk of inheriting the autosomal dominant gene, and a 50% chance of inheriting the normal genes. If both parents are carriers (that is each possess only one unpaired autosomal recessive gene at a location, and accordingly will not express the disease), the first child generally will have a 25% risk of expressing the disease, a 50% chance of being a carrier, and a 25% chance of being normal. Also, see Patricia Baird etal., Genetic Disorders in Children and Young Adults: A Population Study (1988) 42 Am. J. Hum. Genet. 677. From a sample group of more than 1 million consecutive live births, single-gene disorders consisted of 3.6/1000, further broken down to autosomal dominant 1.4 /1000, autosomal recessive 1.7/1000, and X-linked disorders 0.5/1000. Chromosome anomalies constituted 1.8/1000, and multifactorial disorders 46.4/1000.

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