Medic 210 Ch11 (1) PDF

MEDIC 210 CHAPTER 11 MAYRA GONZALEZ RN MSN OBJECTIVES ¡ LO 11.1Discuss family history as a predictor of disease risk. ¡ LO 11.2Identify appropriate uses for DNA testing, and explain how such tests might lead to genetic discrimination. ¡ LO 11.3Define genetic engineering, and explain why cloning...

MEDIC 210 CHAPTER 11 MAYRA GONZALEZ RN MSN OBJECTIVES ¡ LO 11.1Discuss family history as a predictor of disease risk. ¡ LO 11.2Identify appropriate uses for DNA testing, and explain how such tests might lead to genetic discrimination. ¡ LO 11.3Define genetic engineering, and explain why cloning and stem cell research are controversial issues. ¡ LO 11.4Explain three possible remedies for couples experiencing infertility problems. ¡ LO 11.5List those laws affecting health care that pertain especially to children’s rights. VOCABULARY ¡ You know by now that the above examples reflect an individual’s heredity—the process by which genetic traits are passed on to one’s offspring. At this point in your life, you have also learned that genetics is the science that accounts for differences and resemblances among people—and other organisms—related by descent. ¡ As a result of genetics research, improved science education, and extensive media coverage of genetics issues, most of the general population, and certainly anyone involved in providing health care, is now familiar with the term DNA (deoxyribonucleic acid). DNA makes up chromosomes (see Figure 11-1). ¡ The entire DNA strand is billions of base pairs, or rungs, long. Fortunately, an organism does not need to read and interpret the entire DNA strand each time it needs to build proteins. Instead, the organism needs to access only a small part of the DNA, called a gene, to build the protein for which it carries the code. Some genes are only a few hundred base pairs long, whereas others may be several million base pairs long. FIGURE 11.1 DNA ¡ The relationship between the DNA one inherits from ancestors and diseases and other health problems that recur in families has been scientifically confirmed. Although there are many possible causes of human disease, family history is often one of the strongest risk factors for common disease complexes such as cancer, cardiovascular disease, diabetes, autoimmune disorders, and psychiatric illnesses. In addition to the inheritance of a complete set of genes from each parent that may or may not carry the code for disease, a person also inherits a vast array of cultural and socioeconomic experiences from family that minimize or maximize the risk for health problems. DNA CONTINUED ¡ Forty-six chromosomes (23 pairs) are found inside the nucleus of every human cell, except egg and sperm cells, which have 23 chromosomes each. We inherit half of our chromosome complement from our mother and half from our father. These 46 chromosomes carry the genes Page 281responsible for all our human characteristics, from eye, skin, and hair color to height, body type, and intelligence. Each gene is a tiny segment of DNA that holds the formula for making a specific enzyme or protein ¡ The genes that make up the human genome—all the genetic information necessary to create a human being—are responsible for all the cells, organs, tissues, and traits that make up each individual. THE HUMAN GENOME ¡ The Human Genome Project, funded by the U.S. government, was started in 1990 to analyze the entire human genome. Scientists around the world who worked on the project set out to map all of the genes within the 23 pairs of human chromosomes. The project was scheduled for completion in 2003 but was finished ahead of time, in mid-2000. One surprising finding was that instead of a suspected 100,000 genes, humans have approximately 20,000 to 25,000 genes TESTING DNA ¡ Predictive testing. This testing is used to see if genes are present that could lead to hereditary diseases or other harmful genetic conditions. Individuals who come from families in which certain inherited diseases have appeared may opt for predictive genetic testing to confirm or rule out the presence of a disease- causing gene. For example, Huntington’s disease (also known as Huntington’s chorea) runs in families, but symptoms typically do not develop until individuals reach middle age. Because the disease is incurable, debilitating, and fatal, affecting the brain and the nervous system, adults with relatives who have developed the disease may opt to be tested to plan for any eventuality. (Steve, in the chapter’s opening scenario, was considering predictive genetic testing to determine if his genome included variations of the APOE gene associated with the development of Alzheimer’s disease.) ¡ Carrier testing. Used to determine if individuals carry harmful genes that could be passed on to offspring. MORE TESTING ¡ Prenatal testing. This testing is used to identify genetic disorders in utero. Ultrasound, a noninvasive test used since the 1960s, allows for detecting some abnormalities in the fetus, but results must be confirmed with a diagnostic test. Amniocentesis, performed 15 to 20 weeks into pregnancy and also used since the 1960s, can identify chromosomal abnormalities, inherited diseases, and certain developmental defects, but the test involves withdrawing amniotic fluid via a needle extraction through the mother’s abdomen and carries some risk to the fetus. Chorionic villus sampling, developed in the 1980s, involves inserting a needle through the pregnant belly or a catheter through the cervix to suction cells from the placenta. It is performed 10 to 13 weeks into a pregnancy and also carries some risk to the fetus. Since 2011, maternal blood tests have been developed for use Page 283at 10 weeks’ gestation or later that allow testing for chromosomal abnormalities with no risk to the fetus. Because maternal blood contains fetal DNA that has passed through the placenta, testing the mother’s blood can reveal chromosomal abnormalities in the fetus. ¡ Preimplantation testing. These tests look for harmful genes in embryos after artificial insemination but before implantation. They are usually offered to couples who have a reasonable chance of passing on harmful genes. AND MORE TESTING ¡ Forensic testing. Forensic testing is used in law enforcement to eliminate or designate suspects in a crime, identify homicide victims, or otherwise analyze DNA samples for law enforcement purposes. ¡ Tracing lineage. This testing is used in determining parentage or other relationships within families. ¡ Newborn screening tests. These tests are usually performed routinely to check for treatable, harmful genetic conditions or diseases, such as phenylketonuria (see Table 11-1). ¡ Diagnostic testing. Health care practitioners can use DNA testing to confirm a diagnosis, including confirming or ruling out certain genetic diseases. ¡ Medical treatment determination. These tests look for changes or variants in the genes that dictate how medications are processed to determine whether or not a certain medication will be effective in a specific patient, set the best dose for a specific patient, or determine for each individual tested if side effects from a medication are likely. While one’s genome doesn’t change, the test must be performed for each medication prescribed. Similarly, a cancerous tumor’s DNA can sometimes be analyzed to determine which treatment will be most effective in stopping its growth. The science involved is called pharmacogenetics or pharmacogenomics, and it is discussed in more detail in GENETIC DISEASE ¡ Permanent changes in DNA, or mutations, often cause genetic diseases. Mutations can involve one gene, as in sickle cell anemia, hemophilia, cystic fibrosis, Aicardi syndrome, and Huntington’s disease, or they can involve more than one gene. When more than one gene is involved, environmental factors, such as the changes caused by aging, smoking, exposure to environmental toxins, or other factors, may trigger the onset of a genetic disease, as in cases of Alzheimer’s disease, diabetes, obesity, and some forms of cancer. Another type of genetic disease can arise from abnormalities in the structure or number of whole chromosomes. Down syndrome, for example, results from an extra copy of chromosome 21. ¡ Health care practitioners should refer any patient who wants to undergo genetic Page 284testing to a genetic counselor. Genetic counselors can explain test results and help patients deal with difficult questions concerning those results. GENETIC DISCRIMINATION **** READ ¡ With the increased ability to identify genetic differences comes increasing concern for the proper use of such information. The term genetic discrimination describes the differential treatment of individuals based on their actual or presumed genetic differences. ¡ Many people fear that participating in genetic research or undergoing genetic testing will cause them to be discriminated against based on their genetics. Such fears may keep patients from volunteering to participate in the research necessary for the development of new tests, therapies, and cures or may cause them to refuse genomics-based clinical tests. To address this, in 2008, the Genetic Information Nondiscrimination Act (GINA) was passed into law, prohibiting discrimination in the workplace and by health insurance issuers. In addition, there are other legal protections against genetic discrimination by employers, issuers of health insurance, and others. ¡ In addition to GINA at the federal level and state laws against genetic discrimination, the Health Insurance Portability and Accountability Act (HIPAA), passed in 1996, prevents health insurers from denying coverage based on genetic information. HIPAA, however, applies only to individuals moving between group health insurance plans. GENETIC DISCRIMINATION CONT… ¡ The Americans with Disabilities Act (ADA) of 1990, discussed in Chapter 10, also offers some protection against genetic discrimination in the workplace. It protects against discrimination those who have a genetic condition or disease, or are regarded as having a disability. Under a 1995 ruling by the Equal Employment Opportunities Commission, the ADA applies to anyone who is discriminated against on the basis of genetic information relating to illness, disease, condition, or other disorders. Furthermore, under the ADA, a person with a disability cannot be denied insurance or be subject to different terms or conditions of insurance based on disability alone, if the disability does not pose increased risks. GENETIC GEGINEERING ¡ This is called genetic engineering. Because the chemical composition of DNA is nearly identical throughout the plant and animal kingdoms, genes can often be interchanged among plants and animals to transfer desirable characteristics to different Page 286species. Through this process, for example, genes from a species of Arctic flounder have been added to strawberry plants to make them better able to withstand cold temperatures. Genetic engineering has also created corn and soybean crops that are resistant to insect-borne diseases, “golden” rice with increased beta-carotene content, and bacteria that can devour oil spilled into oceans. CLONE ¡ One type of genetic engineering that is rapidly advancing is cloning. Cloning describes the processes used to create an exact genetic replica of another cell, tissue, or organism. The clone is produced asexually, from a single ancestor, and has the same genetic makeup as the original. ¡ There are three different types of cloning: ¡ Gene cloning, which produces exact copies of the segments of DNA called genes. There are two main reasons why geneticists want to clone genes. The first reason for cloning genes is to gain information Page 288about the nucleotide sequence of the gene. A second reason is to manipulate a gene, either by altering its DNA sequence or by combining it with new DNA mixtures, which might mean placing the gene inside the DNA of a different organism. Both of these research objectives require having multimillion copies of genes available for study, and cloning is a way to ensure that exact replicas of the genes are produced. ¡ Therapeutic cloning, which produces copies of embryonic stem cells with the professed purpose of repairing injured or diseased tissue in the human body. Stem cells are early embryonic cells and adult cells derived from certain tissues that have the potential to become any type of body cell. Multipotent stem cells, such as those found in adult blood-forming tissue, can become only a limited number of types of tissues and cells in the body. Pluripotent stem cells, found in embryonic tissue, can become almost all types of tissues and cells. Such cells have shown promise for treating patients with a wide variety of medical problems, such as Parkinson’s, Alzheimer’s, diabetes, strokes, burns, spinal cord injuries, and other neurological disorders. Most embryos used in stem cell research in the United States are the frozen products of in vitro fertilization that were not used to CLONE CONT…. ¡ Reproductive cloning, which produces copies of entire animals. The most famous clone was a Scottish sheep named Dolly. Dolly was created in 1996 from a single maternal cell and lived until 2003, when she was put down to prevent further suffering from a progressive lung disease. She had also developed arthritis, leading to speculation that she aged more quickly than normal. ¡ Scientists have since cloned more sheep, cattle, goats, mice, dogs, cats, monkeys, and pigs. Some lived normal life spans, while others, like Dolly, died young, suffering from conditions usually associated with aging. ¡ Genetically modified farm animals may be bred to develop a consistent source of prime, low-fat meat and other animal products, and some researchers hope cloning can lead to restoring endangered and extinct species. Animal cloning has also been done with human health and medical objectives in mind. For example, genetically modified mice are used extensively as models of human disease, including obesity, substance abuse, anxiety, cancer, and cardiovascular disease. Researchers may spend years developing a strain of mouse with the exact genetic mutations necessary to model a particular human disorder. EXCEPTIONS TO THE RULE ¡ Another objective of cloning genetically modified animals is to breed strains that can produce substances useful in medicine, such as insulin and growth hormone, or to clone animal tissues and organs for human medical use. For example, because pigs are similar to humans in organ size and other biological aspects, an objective in cloning them is to grow a potential source of organs and tissues for transplanting into human patients—a process called xenotransplantation. ¡ Page 289Many animal rights proponents object on ethical grounds to using animals in this way. They argue that animals should be allowed to exist in nature without being subjected to experiments for the benefit of humankind. Furthermore, other groups object to introducing animal cells into humans on ethical grounds and on grounds that the animal tissue can harm people. ¡ Objections against animal cloning are sometimes also based on grounds that such experiments could lead to the cloning of humans, a process that is illegal in the United States and 30 other countries. Objections to human cloning based on animal biology and physiology include: CLONE CONT … ¡ To date, animal cloning does not always yield viable offspring, with only one or two healthy animals resulting from approximately every 100 experiments. ¡ Not only do most attempts to clone mammals fail, about 30 percent of clones born alive are affected with “large-offspring syndrome” and other debilitating conditions. Large-offspring syndrome occurs primarily in cloned lambs and calves that are the result of embryo manipulation. The process often creates oversized offspring due to deactivation of insulin-like growth factor 2 receptors, which would normally block the growth of cells at a certain point. When these receptors are deactivated, the embryos grow too large. Other symptoms can include enlarged hearts, immature lungs, and damaged kidneys. ¡ Scientists do not yet understand the processes involved in reproductive cloning well enough to ensure success, and a large failure rate in human clones is unacceptable. ¡ Like Dolly the sheep, many cloned animals have died prematurely from infections and other complications. The same problems would be expected to occur in human cloning. ¡ Scientists do not know how cloning could impact mental development. While factors such as intellect and mood may not be important for a cloned cow or mouse, they are crucial for the development of healthy humans. ETHICAL CONCERNS ¡ Ethical questions multiply when human cloning is discussed. Should trial and error over time be allowed when the objective is to create a healthy human baby? Besides the potential for physical problems over numerous tries, even if a viable human is finally produced, how would families handle the supercharged family dynamics that might result? For example, what if a couple divorces after a child has been cloned to resemble one parent? Will the other parent resent the child who looks so much like the divorced spouse? On a broader level, would cloning be reserved only for the wealthy who can afford the process and denied to all those in a society who cannot pay the fee? ¡ Because such ethical questions would be difficult to resolve, most states have laws banning the cloning of humans, but to date, no federal law has been passed. The latest attempt at federal legislation was HR. 3498 the Human Cloning Prohibition Act of 2105, which was still in committee in mid-2016. GENE THERAPY ¡ Gene therapygene therapy ¡ The insertion of a normally functioning gene into cells in which an abnormal or absent element of the gene has caused disease. ¡ is rapidly becoming an effective tool for correcting and preventing certain diseases. In fact, therapy for genetic disease is often very similar to therapy for other types of disorders, as in the following cases: ¡ Special diets can eliminate compounds that are toxic to patients. This applies to such diseases as phenylketonuria and homocystinuria. ¡ Vitamins or other agents can improve a biochemical pathway and thus reduce toxic levels of a compound. For example, folic acid reduces homocysteine levels in a person who carries the 5,10- methylenetetrahydrofolate reductase polymorphism gene. ¡ Gene therapy may involve replacing a deficiency or blocking an overactive pathway. For instance, a fetus can sometimes be treated by treating the mother (e.g., corticosteroids for congenital virilizing adrenal hypoplasia) or by using in utero (inside the uterus) cellular therapy (e.g., bone marrow transplantation). Similarly, a newborn with a genetic disease may be a candidate for treatment with bone marrow or organ transplantation. GENE THERAPY CONT… ¡ Genetic therapy may also involve the insertion of normal copies of a gene into the cells of persons with a specific genetic disease (this is called somatic gene therapy). Such somatic gene therapy has been undertaken for severe genetic disorders such as adenosine deaminase deficiency, an immunodeficiency that usually results in death during the first few months of life. ¡ Germ-line gene therapy involves the correction of an abnormality in the genes of a sperm or egg but is presently considered an inappropriate way to deal with genetic diseases because of ethical issues, cost, lack of research in humans, lack of knowledge about whether or not changes would be maintained in the growing embryo, and the relative ease of treating the pertinent conditions somatically when needed. INFERTILITY ¡ However, it is estimated that about 10 to 15 percent of reproductive-age couples in the United States will have difficulty conceiving. Of this percentage, either husband or wife will experience infertility—that is, the failure to conceive for a period of 12 months or longer due to a deviation from or interruption of the normal structure or function of any reproductive part, organ, or system. ¡ Several options for infertile couples exist, depending on the type of fertility problem. Here are a few of the most common: ¡ In vitro fertilization. In this process, eggs and sperm are brought together outside the body in a test tube or petri dish. When fertilization takes place, the resulting embryo can then be frozen in liquid nitrogen for future use or implanted in the female uterus for pregnancy to occur. ¡ Artificial insemination. This process involves the mechanical injection of viable semen into the vagina. If a man’s sperm cells are used to fertilize his partner’s eggs, the process is called homologous artificial insemination. If the partner’s sperm cells are not viable, a donor’s sperm may be used to fertilize the woman’s eggs. This is called heterologous artificial insemination. ¡ Surrogacy. If a woman cannot carry an embryo to term, the couple may elect to contract with a surrogate mother. SURROGATE/ ADOPTION ¡ A surrogate mother is a woman who agrees to carry a child to term for a couple, often for a fee. If the surrogate is not genetically related to the embryo, the type of surrogacy is called gestational surrogacy. If the surrogate contributes eggs to produce the embryo or is related to either partner in the relationship, the type of surrogacy is called traditional surrogacy. (In one much-publicized case in the United States, a woman carried her own grandchild to term for her married daughter who was born without a uterus.) Traditional surrogacy differs from gestational surrogacy in that a traditional surrogate is genetically related to the fetus she carries. ¡ Adoption is also an option for those couples who want to raise children. All 50 states have laws regulating adoption. Certain areas of federal law may also affect some aspects of the parent–child relationship established by adoption. For example, the Adoption Assistance and Child Welfare Act of 1980, the Child Abuse Prevention and Treatment and Adoption Reform Act, and the Indian Child Welfare Act all contain provisions that pertain to adoptive parents and their children. CHILDREN'S RIGHTS ¡ Common law has established the rights of parents to make health care decisions for minor children. In some circumstances, under the doctrine of parens patriae, literally “father of the people,” the state may act as the parental authority. This doctrine is the legal principle that grants the Page 294state the broad authority to act in the child’s best interest, sometimes overriding parental decisions, and allows the state to remove abused or neglected children from the custody of offending parents. ¡ Legally, the legal rights of newborns are the same as those of any other American citizen of any age. For newborns who are severely disabled, however, existing law provides for several treatment options. Under the federal Child Abuse Amendments (42 U.S.C. Section 5106g), if the parents agree, physicians may legally withhold treatment, including food and water, from infants who: ¡ Are chronically and irreversibly comatose ¡ Will most certainly die and for whom treatment is considered futile ¡ Would suffer inhumanely if treatment were provided ABANDONMENT ¡ An unfortunate fact of modern life is that there are too many stories in the news of mothers abandoning their infants shortly after giving birth by leaving them in dumpsters, by the roadside, in public restrooms, and so on, usually out of fear or desperation. As such abandonment numbers have increased, all 50 states have enacted safe haven laws that allow a parent to abandon a newborn at a safe location, usually within a specified time limit after birth, and without legal prosecution.