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Genetics and Health - Genetic Inheritance, Genetic Disorders, Genetic Testing, Genetic Testing And Human Reproduction, Genetic Testing In Children And Adults

Even at birth the whole individual is destined to die, and perhaps his organic disposition may already contain the indication of what he is to die from.

—Sigmund Freud, 1924

Genetics, which is the branch of biology that studies heredity, concerns the biochemical instructions that convey information from generation to generation. In order to appreciate the role of genetics in health and illness, it is important to understand the interaction of genes, chromosomes, and genomes and to learn how deoxyribonucleic acid (DNA) functions as the information molecule of living organisms.

Genes are units of hereditary information that are made of DNA and located on chromosomes, which are separate strands of DNA wrapped in a double helix (two intertwined three-dimensional spirals) around a core of proteins contained in the nuclei of cells. Genes contain the instructions for the production of proteins, which make up the structure of cells and direct their activities. They exist in corresponding pairs, and a genome is a complete set of paired genes for an organism. Humans have 46 chromosomes arranged in 23 pairs, and the human genome contains about 30,000 genes and 600,000 pairs of DNA. Changes in the number, size, shape, or structure of chromosomes can result in a variety of physical and mental abnormalities and diseases.

Additional Topics

Genetics and Health - Genetic Inheritance

For inheritance of simple genetic traits, the two inherited copies of a gene determine the phenotype (the observable characteristic) for that trait. When genes for a particular trait exist in two or more different forms that may differ between individuals and populations, they are called alleles. For example, brown and blue eye colors are due to different alleles for eye color. For every gene, the…

Genetics and Health - Genetic Disorders

There are two types of genes: dominant and recessive. When a dominant gene is passed on to offspring, the feature or trait it determines will appear regardless of the characteristics of the corresponding gene on the chromosome inherited from the other parent. If the gene is recessive, the feature it determines will not show up in the offspring unless both the parents' chromosomes contain th…

Genetics and Health - Genetic Testing

A genetic test is the analysis of human DNA, ribonucleic acid (RNA), chromosomes, and proteins in order to detect heritable diseases for the purposes of diagnosis, treatment, and other clinical decision making. Most genetic testing is performed by drawing a blood sample and extracting DNA from white blood cells. There is a broad range of techniques that can be used for genetic testing. Genetic tes…

Genetics and Health - Genetic Testing And Human Reproduction

There are thousands of genetic diseases, such as sickle cell anemia, cystic fibrosis, and Tay-Sachs disease, that may be passed from one generation to the next. Numerous tests have been developed to help screen parents at risk of passing on genetic disease to their children as well as to identify embryos, fetuses, and newborns that suffer from genetic diseases. Carrier identification is the term f…

Genetics and Health - Genetic Testing In Children And Adults

Genetic testing also can be performed postnatally (after birth) to determine which children and adults are at increased risk of developing specific diseases. Scientists can perform predictive genetic testing to identify which individuals are at risk for cystic fibrosis, Tay-Sachs disease, Huntington's disease, amyotrophic lateral sclerosis (ALS; a degenerative neurologic condition commonly…

Genetics and Health - Ethical Considerations And Genetic Testing

Rapid advances in genetic research during the past two decades have challenged scientists, health care professionals, ethicists, government regulators, legislators, and consumers to stay abreast of new developments. Understanding the scientific advances and their implications is critical for everyone involved in making informed decisions about the ways in which genetic research and information wil…

Genetics and Health - Common Genetically Inherited Diseases

Although many diseases, disorders, and conditions are termed "genetic," classifying a disease as genetic simply means that there is an identified genetic component to either its origin or expression. Many medical geneticists contend that the majority of diseases cannot be classified as strictly genetic or environmental. Environmental factors can greatly influence the way disease caus…

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