Newborn Screening (Genetics & Inherited Conditions)
The most widespread use of genetic screening is the testing of newborn babies. The purpose of newborn screening is to provide immediate treatment after birth to affected infants so that the symptoms of a disease can be lessened or prevented.
Screening for phenylketonuria (PKU) began in the 1960’s and is one of the oldest and best-known newborn screening programs. Blood samples are taken from the heels of newborn babies in the hospital nursery, placed on filter papers as dried spots, and sent off to appropriate laboratories for analysis. Newborns with elevated phenylalanine levels can be effectively treated with a diet low in phenylalanine (low-protein foods). If treatment is not initiated within the first two months of life, mental retardation will occur. Individuals with PKU lack the enzyme phenylalanine hydroxylase (PAH), which converts the essential amino acid phenylalanine into the amino acid tyrosine. The lack of the enzyme PAH leads to the accumulation of phenylalanine in the body, which causes irreversible brain damage.
In addition to PKU, the newborn screen can test for other metabolic disorders, endocrine disorders (such as congenital hypothyroidism), blood conditions, deafness, and some acquired perinatal infections. In the United States, differences exist between states in terms of what conditions are screened for on the newborn panel. In 2005, the median number of tests on the newborn screen in each...
(The entire section is 236 words.)
Carrier Screening (Genetics & Inherited Conditions)
Carrier screening is the voluntary testing of healthy individuals of reproductive age who may be carriers for an autosomal recessive disorder. Autosomal recessive disorders occur when an individual inherits a nonworking gene, or mutation, from both of their parents. The parents are called “carriers” because they have one working copy of the gene and one nonworking copy of the gene. Carriers do not exhibit any symptoms of the genetic condition. However, with each pregnancy, two carrier parents have a 25 percent chance for the offspring to inherit the genetic condition.
The risk of being a carrier for an autosomal recessive disorder is often dependent upon one’s ancestry. For example, individuals of African descent have an increased risk of being a carrier for sickle-cell anemia, which is a blood disorder associated with a change in the shape of the red blood cells that can lead to difficulty transporting oxygen around the body. Individuals of Ashkenazi Jewish heritage are at increased risk of being carriers of at least ten genetic conditions. Tay-Sachs disease, which is a progressive neurological condition associated with death in infancy, is one of the best-known conditions for which Ashkenazi Jewish individuals are offered screening.
Historically, people were not always given a choice to have carrier screening. In the early 1970’s, mandatory, large-scale screening of African American couples and some...
(The entire section is 478 words.)
Prenatal Screening (Genetics & Inherited Conditions)
All pregnant women are routinely offered screening tests for chromosome abnormalities such as Down syndrome, the most common chromosome condition. Individuals with Down syndrome have an extra copy of chromosome number 21 that leads to a distinctive appearance, mild-to-moderate mental retardation, and sometimes other medical issues such as heart defects or digestive system problems. The risk of having a baby with Down syndrome increases with a woman’s age, but all women have some risk. Blood and ultrasound tests are routinely offered to all women to determine if the pregnancy is at increased risk for Down syndrome. Women in the high-risk category are offered diagnostic testing such as a CVS or amniocentesis.
(The entire section is 111 words.)
Impact and Applications (Genetics & Inherited Conditions)
With the completion of the Human Genome Project, the number of genetic screening options has grown exponentially. In 2003, the American College of Obstetricians and Gynecologists recommended that providers offer all couples who are pregnant or planning a pregnancy carrier screening for cystic fibrosis, an autosomal recessive multisystem disorder that can affect the lungs, digestive system, and urogenital tract. Most states now also offer newborn screening for cystic fibrosis. In 2008, the American College of Medical Genetics issued a practice guideline stating that providers should offer all couples carrier screening for spinal muscular atrophy, an autosomal recessive neurological disorder. Some experts are advocates for population-based carrier screening for fragile X syndrome, a relatively common genetic form of mental retardation in males that can be carried by females and inherited by their sons. The technology to detect fetal cells in the maternal bloodstream is rapidly evolving, and soon pregnant woman may be able to learn if their fetus has Down syndrome with a simple blood draw.
As new tests are added to routine screening protocols and further tests are considered for population screening, society is faced with the ethical dilemma of deciding what makes a disease a candidate for genetic screening. In order for a disease to be considered for a population screening program, certain factors must exist. Some are...
(The entire section is 418 words.)
Further Reading (Genetics & Inherited Conditions)
Chadwick, Ruth, et al., eds. The Ethics of Genetic Screening. Boston: Kluwer Academic, 1999. Discusses the ethical principles of genetic screening programs, describes genetic screening programs in European nations, and analyzes social and historical conditions that influence national programs.
Evans, Mark I., ed. Metabolic and Genetic Screening. Philadelphia: W. B. Saunders, 2001. Covers principles of screening, screening for neural tube defects, second-trimester biochemical screening, prenatal genetic screening in the Ashkenazi Jewish population, cystic fibrosis, identifying and managing hereditary risk of breast and ovarian cancer, and genetic implications for newborn screening for phenylketonuria.
Heyman, Bob, and Mette Henriksen. Risk, Age, and Pregnancy: A Case Study of Prenatal Genetic Screening and Testing. New York: Palgrave, 2001. Provides a detailed case study of a prenatal genetic screening and testing system in a British hospital, giving perspectives of pregnant women, hospital doctors, and midwives, and elucidating the communication between women and the hospital doctors who advise them.
Nussbaum, Robert, et al. Genetics in Medicine. 6th ed. Rev. reprint. Philadelphia: Thompson & Thompson, 2004. Comprehensive review of the fundamental principles in medical genetics for medical professionals. The last chapter contains detailed information about genetic...
(The entire section is 303 words.)
Web Sites of Interest (Genetics & Inherited Conditions)
American College of Medical Genetics. http://www.acmg.net. Frequently updated Web site for public and professionals sponsored by ACMG.
American Medical Association. http://ama-assn.org. The AMA’s guidelines on the ethics of genetic screening.
Centers for Disease Control: Genomics and Disease Prevention. http://www.cdc.gov/genomics/info/reports/program/population.htm. A journal article on genetic screening, entitled “Population Screening in the Age of Genomic Medicine.”
Genetics Home Reference. http://ghr.nlm.nih.gov. Site by National Institutes of Health that contains resources on a multitude of genetic conditions as well as information about genetic screening.
National Society of Genetic Counselors. http://www.nsgc.org. Web site for professional organization of genetic counselors; contains position statements about genetic screening.
(The entire section is 122 words.)
Genetic Screening (West's Encyclopedia of American Law)
The scientific procedure of examining genetic makeup to determine if an individual possesses genetic traits that indicate a tendency toward acquiring or carrying certain diseases or conditions. In 2001, scientists first published the complete human genome map (a human's genetic blueprint), greatly advancing the capability and use of genetic screening, manipulation, and replication.
Genetic testing of humans facilitates the discovery and treatment of genetic defects, both before and after birth. CIVIL RIGHTS proponents, employers, and those who suffer from genetic diseases have debated genetic screening because the procedure poses practical and theoretical legal, economic, and ethical problems. Some theorists, for example, have suggested that genetic screening could improve society if it were made mandatory before hiring or marriage. Others say that this practice would be unconstitutional. Genetic screening is a dynamic rather than static field of medical and scientific experimentation and application that clearly involves scientific, legal, and ethical interests which may differ or compete. Accordingly, each new milestone or discovery warrants commensurate review of these interests for both beneficial and potentially detrimental consequences.
Federal and State Legislation
The earliest national and state legislation concerning genetic screening...
(The entire section is 1709 words.)