1 Human Behavior and the Social Environment: Theories for Social Work Practice Bruce A. Thyer, Catherine N. Dulmus, and Karen M. Sowers, Editors Chapter 8 Genetic Theory by Laura J. Pankow Human genetics is the study of inheritance, of how features possessed by one’s parents are passed on to one’s biological children. Genetic influences are largely responsible for our physical features as well as aspects of our temperament and abilities. Environmental influences during pregnancy (e.g., maternal diet and illness) and after birth can modify the expression of our genetic endowment. Someone born of very tall parents might have stunted growth due to dietary deficiencies, for example. Social work has had a long-standing interest in the role of inheritance and genetics and there is a modest literature on the topic. The National Association of Social Workers has produced some practice standards for social workers involved in helping clients with genetic disorders and their families. Seehttp://

2 Human Behavior and the Social Environment: Theories for Social Work Practice Bruce A. Thyer, Catherine N. Dulmus, and Karen M. Sowers, Editors Chapter 8 Genetic Theory by Laura J. Pankow Although it has long been known that parental features are passed on to offspring (e.g., animal breeders have selectively breed livestock with desired features for years; farmers selectively breed more productive and disease-resistant crops), the scientific study of modern genetics got its start with the botanical studies of Gregor Mendel (1822–1884), an Austrian monk, who studied plants, and how characteristics such as height and color were transmitted across generations. Mendel quantified how traits were passed on, but he did not develop a satisfactory mechanism to explain how this occurred. It was not until Watson and Crick published a 1953 paper in the journal Nature that the correct mechanism was discovered through which genes carrying DNA were said to be responsible for the phenomenon of inheritance. Their one-page paper, for which the authors received a Nobel Prize, can be located here:

3 Human Behavior and the Social Environment: Theories for Social Work Practice Bruce A. Thyer, Catherine N. Dulmus, and Karen M. Sowers, Editors Chapter 8 Genetic Theory by Laura J. Pankow DNA stands for deoxyribonucleic acid and under a microscope appears to be structured as a ladder that is twisted into a spiral helix. The sides of this molecular ladder are made up of sugars and phosphates and the rungs are composed of amino acids. Sections of DNA are called genes and carry information which structures how cells reproduce and transmit traits. One DNA molecule has many genes. DNA is contained within the nucleus of the body’s cells in structures called chromosomes. When cells divide (reproduce) the chromosomes and their DNA (hence gene structure) is duplicated. In humans, the gonads (ovaries in women and testes in men) carry the DNA that is involved in reproduction. The ovary produces eggs (ova) containing the woman’s DNA, and the testes produce sperm, which contains the man’s DNA. When the sperm fertilizes the egg, the egg contains genetic information from both parents.

4 Human Behavior and the Social Environment: Theories for Social Work Practice Bruce A. Thyer, Catherine N. Dulmus, and Karen M. Sowers, Editors Chapter 8 Genetic Theory by Laura J. Pankow Male babies possess an X chromosome from the mother and a Y chromosome from the father. Female babies possess an X chromosome from each parent. Thus the father determines the gender of the baby. Almost all male babies possess an X and a Y chromosome, and females a XX pair. However genetic diseases are the result of abnormal numbers of X and Y chromosomes. Individuals possessing an X chromosome but who lack a Y chromosome display Turner’s Syndrome. Someone with with an XXY pattern will display Klinefelter’s Syndrome. Fragile X Syndrome is caused by being born with an XY combination, but where one of the arms of the X chromosome is constricted. Hemophilia, a blood disorder characterized by impaired clotting ability, is an X- linked genetic condition, as are forms of color-blindness. Some genetic disorders are more common in certain groups. Persons of African descent are at much higher risk to develop sickle-cell anemia, while Tay-Sachs disease is more common among persons of eastern European Ashkenazi Jewish descent.

5 Human Behavior and the Social Environment: Theories for Social Work Practice Bruce A. Thyer, Catherine N. Dulmus, and Karen M. Sowers, Editors Chapter 8 Genetic Theory by Laura J. Pankow Some social workers specialize in genetic counseling, helping potential parents who may be carrier of a genetic disorder, decide to have or not to have children. Others provide psychotherapy to individuals with genetic disorders such as Huntington’s Disease, a form of cognitive impairment that does not usually manifest until midlife. Some forms of developmental disability are genetically based and many social work services are provided to such persons and their families, across the life span. A general knowledge of genetic theory is important for all social workers to possess, and those serving clients with genetic illnesses need an in-depth background to be effective helpers. Some social workers join the National Society of Genetic Counselors to obtain advanced expertise in this area. See: It is hoped that advances in genetic research will eventually lead to gene-based therapies, or even effective treatments for persons with a genetic disease. It is also hoped that at some point it may be possible to correct a genetic abnormality among carriers.