Genetics: Analysis of Genes and Genomes: Keyword Hot Links for chapter 18

This keyword will open a table of frequencies of the most common types of birth defects in the U. S. population. The overall frequency of these conditions is about one in 25 births. Most of the conditions that have genetic risk factors are complex traits affected by multiple genes; these include disorders of the heart and circulation, muscles and skeleton, genital and urinary tract, and nervous system and eye, which together have an incidence of one in 35.

Older genetics textbooks often reported that blue eye color versus brown eye color in human beings has a simple Mendelian mode of inheritance, with blue eyes recessive to brown. This hypothesis is still widely disseminated in elementary and high school textbooks. For the latest information on the inheritance of eye color, log onto this keyword site .

Many human disorders are complex, multifactorial traits with significant genetic components as well as multiple environmental factors in their causation. The identification of the specific genetic and environmental causes of such conditions is extremely difficult. A case in point is schizophrenia, a relatively common mental disease with an estimated incidence of 1–1.5% in the U. S. population. Though serious, schizophrenia is usually treatable with drug therapy. Schizophrenia appears to have a significant genetic component, and there are probably multiple forms of the disease. At this keyword site you can learn more about this condition and the meaning of the statement: "People do not cause schizophrenia; they merely blame each other for doing so."

The keyword serotonin will link you to a site offering a three-dimensional display of over 200,000 small biological molecules, including Prozac® and serotonin. Using the mouse, the structures can be tilted and rotated to analyze the spatial relationships among the atoms. Use this site to compare the three-dimensional structures of 5-hydroxy-tryptamine (serotonin) and fluoxetine (Prozac®), which can be found in the indices for biomolecules and for pharmaceuticals–prescription drugs, respectively. It is also interesting to compare melatonin with these structures. Melatonin is involved in maintaining our circadian rhythms.