Overview of the Immune System

The immune system includes several interacting components. Nonspecific immunity (protection against any invasion) is provided by the barriers of the skin and mucous membranes lining the lungs and gut. Additional nonspecific defenses are provided by the inflammatory response and the complement proteins in the bloodstream. We shall not deal further with these defenses. Specific immunity is the set of defenses mounted against a specific invader. It involves the action of three major types of cells...

Positive and Negative Eugenics

Galton identified positive and negative eugenics as the two basic methods to improve humanity. Positive eugenics used education, tax incentives, and childbirth stipends to encourage procreation among fit people. Education would convince fit parents to have more children, out of a desire to increase the common good. Lower taxes on larger families and the provision of a small birth payment for each eugenic child would provide further inducements. Conversely, eugenically educated but unfit people...

Autosomal Dominant Inheritance

Autosomal dominant inheritance is due to a dominant allele carried on one of the autosomes. Autosomal dominant alleles need only be inherited from one parent, either the mother or the father, in order to be expressed in the phenotype. Because of this, any child has a 50 percent chance of inheriting the allele and expressing the trait if one parent has it. Many normal human traits are due to autosomal dominant alleles, including the presence of dimples, a cleft chin, and a widow's-peak hairline....

Linking Subunits into Chains

Mineral catalysts have also been useful in forming chains of RNA-like molecules from the activated precursors. James Ferris has focused on the ability of montmorillonite (a type of clay) to promote the assembly of the ribose-phosphate backbone, starting with a special, uracil-containing compound known as a phosphorimidazolide. Although phosphorimidazolides do not occur in nature today, they are highly reactive species and closely related to the modern building blocks of RNA. Most scientists do...

Presymptomatic Testing of Children

Presymptomatic testing of children has somewhat different considerations. It is typically considered only when the onset of the disorder occurs in childhood, or when knowing the genetic status will significantly benefit the child, for example by enabling him to receive early preventive treatment. For example, children at risk for inheriting the gene that causes retinoblastoma (cancer of the retina) may be tested because the disease usually presents before age five. With early treatment, the...

Metabolism

Despite the lack of internal compartmentalization, bacterial metabolism is complex, and is far more diverse than eukaryotic metabolism. Within the Eubacteria there are species that perform virtually every biochemical reaction known (and much bacterial chemistry remains to be discovered). Most of the vitamins humans require in our diet can be synthesized by bacteria, including the vitamin K humans absorb from the Escherichia coli (E. coli) bacteria in our large intestines. The broadest and most...

The Importance of SNPs

Genomic medicine will be applied to patients through several mechanisms. polymorphisms DNA The primary tool will be the detection of single nucleotide polymorphisms (SNPs). These are small variations in DNA sequences that are found in every person. These normal polymorphisms are very frequent, occurring in approximately one out of every 1,000 base pairs. The majority of these SNPs occurs in regions of the genome that do not code for proteins, and usually do not contribute to a person's disease...

Susceptibility Testing Apolipoprotein E

Susceptibility testing is another area that raises possible ethical issues for patients and clinicians. Recall that susceptibility implies that the genetic test does not provide the final answer regarding disease, but rather that additional factors are involved. For example, cardiovascular disease is a major source of morbidity and mortality. Polymorphic variants in the apolipoprotein E gene (APOE) have been found to be associated with variations in blood levels of lipids, lipoproteins, and...

Mendelian Inheritance Intelligence Testing and American Eugenics

Galton's eugenic ideas found fertile ground in America after 1900, when scientists rediscovered Mendel's findings regarding the inheritance of physical traits in pea plants. Mendel's notions of dominant and recessive genetic traits, easily identified in lower organisms such as plants and animals, convinced people that human eugenic improvement was possible. Scientists assumed that even complex human traits such as intelligence and behavior behaved as simple genetic unit characters, such as...

The Future of Medicine

The idea of preventive medicine is not new, but until the completion of the Human Genome Project medicine did not have a way of accomplishing it for common medical problems. For example, for years almost every baby born in the United States has had its urine or blood screened early in life for phenylketonuria PKU , a rare genetic disease in which affected individuals cannot metabolize the amino acid phenyalanine, a common amino acid in our food. Untreated, PKU patients develop severe mental and...