Chromosomal Basis of Down Syndrome

In 1959 French geneticist Jerome Lejeune recognized that individuals with Down syndrome have forty-seven chromosomes instead of the usual forty-six. Later, it was determined that it is an extra copy of chromosome 21 that causes the condition. It is not yet clear how the extra chromosome causes the clinical features, although it is believed that an extra dose of one or more of the genes on the chromosome is responsible. Down syndrome is a chromosome disorder that causes mental retardation....

Chaperones and Human Disease

It is clear that molecular chaperones assist with the folding of newly synthesized proteins and correct protein misfolding. Recent studies now suggest that defects in molecular chaperone substrate interactions may also play a substantial role in human disease. For example, mutations linked to Alzheimer's disease have been shown to disrupt the expression of chaper-ones in the endoplasmic reticulum. In addition, several genes linked to eye degeneration diseases have recently been identified as...

Maternal Conditions

Birth defects can also result from physical conditions affecting the health of the mother. One common maternal condition associated with birth defects is diabetes mellitus, a multifactorial disorder. Mothers with diabetes have a two- to three-fold times greater risk of having a child with birth defects than the general population if their condition is not well controlled. However, good glucose control has been shown to correlate with a decreased risk of congenital malformations. Characteristic...

Education and Training

Crick was born in Northampton, England, in 1916. He studied physics at University College in London until the outbreak of the Second World War. He then joined the British Admiralty Research Laboratory, where he contributed to the development of radar for tracking enemy planes, and magnetic mines used in naval warfare. During this time, Crick read What is Life , a book by the physicist Erwin Schr dinger. Schr dinger's book popularized the work of physicist Max Delbr ck, who had begun to apply...

Classification of Cancer Types

The term cancer is general, in that it represents a large group of related diseases that arise from neoplasms. A neoplasm is classified by the type of tissue in which it arises and the stage to which it has progressed. Neoplasms are also called tumors. Not all tumors are cancerous. A tumor that grows in one place and does not invade surrounding tissue is called benign. In contrast, invasive tumors are called malignant. These are cancerous. ESTIMATED NEW CANCER CASES AND DEATHS IN THE UNITED...

Rationale for a Genetic Approach to Alzheimers Disease

Alzheimer's disease, broadly defined, is a complex genetic disorder Multiple causative and susceptibility genes acting singly or in concert produce similar symptoms and pathologic changes in patients. In each of its forms, it manifests age-dependent penetrance, meaning that the older an individual becomes, the more likely it is that he or she will develop the disease. Disease manifestations (such as age of onset or rate of progression) may be influenced by environmental exposures (alcohol use,...

Disorders Associated with Aneuploidy

Three well-known autosomal chromosome disorders associated with trisomies of entire autosomes are sometimes found in live births. These are trisomy 21 (Down syndrome), trisomy 13, and trisomy 18. Growth retardation, mental retardation, and multiple congenital anomalies are associated with all three trisomies. However, each has distinctive morphological characteristics, which are presumably determined by the extra dosage of the specific genes on the additional chromosome. Down syndrome...

An Evolving Understanding of Dementia

Within three years of the publication of Dr. Alzheimer's first case, the term Alzheimer's disease was applied to patients who developed significant difficulty in memory and other areas of cognition at an age less than sixty-five years. Individuals who developed such symptoms later in life, generally after the age of sixty-five, were said to be suffering from senility, a process stroke, aneurysm, or other circulatory disorder affecting the brain

Finding Genes for Cardiovascular Disease

Genetics studies of cardiovascular disease involve searches for genes in two general classes causative genes and disease-susceptibility (or disease-modifying) genes. These are sought through gene-linkage analysis or candidate-gene studies, respectively. Identifying causative genes for this disease is likely several years away at best. Before that time, however, a new understanding will have been reached regarding the relationship between inherited risks and outcomes in cardiovascular disease....

Genetic Susceptibility to Complications

As mentioned above, diabetes is associated with complications involving the eyes, kidneys, blood vessels, and heart. However, not all individuals with diabetes develop these complications. There is increasing evidence that there are genes other than those that increase susceptibility to developing the disease that may influence susceptibility to developing its complications. These genes are not yet identified, but they are likely to interact with other known risk factors for complications,...

The Range of Androgen Insensitivity Syndromes

AIS occurs in a range of forms, from complete to mild. Most mutations to the testosterone-binding region, and some other types of mutations, cause complete androgen insensitivity syndrome (CAIS). In this form of the syndrome, the XY person is born phenotypically female, and from birth is raised as a girl. Gender identification (the internal sense of being male or female) is female. Sexual orientation is typically heterosexual, and so most CAIS individuals are attracted to males. At puberty,...

Oooocoo

Clubbed feet (talipes equinovarous) result from abnormal development of the muscles, tendons and bones of the feet in utero. Heredity is thought to play a role when such deformities appear. viruses, and can affect a fetus from as early as the first few weeks after conception through the second trimester. For this reason, ideally, women should avoid all medications during pregnancy. However, in some circumstances there are medical risks and benefits that must be weighed, particularly if a...

Complex Behaviors Complex Causes

Thus, for use and abuse of alcohol, we know that the importance of genetic and environmental effects changes with sequencing in the use and abuse of alcohol, from abstinence or initiation to frequency of regular consumption, to problems associated with consumption, and ultimately, to diagnosed alcoholism and end-organ damage from the cumulative effects of alcohol. Similar stories could be told for many other behaviors of interest. Thus, for the major psychopathologies, from depression and...

The Genetic Epidemiology of ADHD

Family, twin, and adoption studies provide strong support for the idea that genes influence the etiology of ADHD. Family studies find the parents and siblings of ADHD children to have a five-fold increase in the risk for ADHD. Children of ADHD adults have a ten-fold increase in risk, which has led to the idea that persistent cases of ADHD may have a stronger genetic component. Consistent with a genetic theory of ADHD, second-degree relatives (such as cousins) are at increased risk for the...

Patents and the Rise of Biotechnology Companies

Supreme Court provided an important incentive for the development of biotechnology companies. In the case of Diamond v. Chakrabarty, the court ruled that biological materials may be patented. Thus, private companies could look forward to making substantial profits from therapies that they developed through genetic engineering techniques. Among the new companies to take advantage of the court ruling was the Chiron corporation, which cloned the protein that formed the outer coat...

Ooocx

Antigen a foreign substance that provokes an immune response plasmid a small ring of DNA found in many bacteria biolistic firing a microscopic pellet into a biological sample (from biological ballistic) Tang, D. C., M. Devit, and S. A. Johnston. Genetic Immunization Is a Simple Method for Eliciting an Immune Response. Nature 356 (1992) 152-154. Ulmer, Jeffrey B., John J. Donnelly, and Margaret A. Liu. DNA Vaccines Promising A New Approach to Inducing Protective Immunity. ASM News 62 (1996)...

Chromosome Disorders

Humans normally have twenty-two pairs of autosomes and two sex chromosomes, XX or XY, making forty-six chromosomes in total. Chromosomal abnormalities occur in about 0.5 percent of all live births and are usually due to an abnormal number of chromosomes. These are nearly always an addition or deletion of a single autosome or sex chromosome in a pair. One extra copy of a chromosome is called a trisomy, while one missing copy of a chromosome is called a monosomy. Sometimes only a segment of a...

Hereditary Nonpolyposis Colon Cancer

HNPCC is an autosomal dominant disorder that may be responsible for up to 5 percent of colon cancers. The genetic mutation leading to the abnormality is the mutation of DNA mismatch repair genes. Individuals with this mutation have up to an 80 percent chance of developing colon cancer. At least five genes are involved in this syndrome. Malignancy in patients with HNPCC occurs at a younger age than in the general population, is more often located in the proximal colon (the portion nearest the...

Table of Contents

Preface For Your Reference ix List of Contributors xvii Accelerated Aging Progeria 1 Addiction Aging and Life Span Agricultural Biotechnology 9 Alternative Splicing Alzheimer's Disease Ames Test Androgen Insensitivity Syndrome 21 Antibiotic Resistance Antisense Nucleotides 29 Apoptosis Arabidopsis thaliana Archaea Attention Deficit Hyperactivity Disorder 39 Attorney Automated Sequencer 43 Balanced Polymorphism 45 Behavior Bioinformatics Biopesticides Bioremediation Biotechnology Biotechnology...

Deregulation and Cancer

Deregulation of cell cycle control proteins plays a key role in the development of cancer. Overactivation of proteins that favor cell cycle progression, namely cyclins and CDKs, and the inactivation of proteins that impede cell cycle progression, such as CKIs, can result in uncontrolled cell proliferation. In human tumors, it is genes encoding the proteins that control the transition from the G1 to the S phase that are most commonly altered. These genes include those for cyclins, CKIs, and pRb....

Antibiotic Resistance

From the human perspective, one of the significant consequences of a bacterium's ability to pass genetic information along to other cells via conjugation is its link to the widespread incidence of antibiotic resistance. The genes that encode for resistance to a variety of antibiotics like penicillin and tetracycline are commonly found on plasmids. When a population of susceptible bacteria is exposed to a given antibiotic, most of them will be killed. However, if the population contains cells...

Illustrative Examples

Blotting is perhaps best understood with illustrative examples. Suppose a student was studying a newly identified gene, X, from cows. The student then asks three basic questions as part of a research project (1) Do pigs also have gene X on their chromosomes (2) Do cows express gene X in their brain tissue (3) Is the protein product of gene X found in the cow's blood plasma Blotting experiments can answer all three of these questions. nucleotide the building block of RNA or DNA antibodies...

How the Environment Is Involved in Complex Disease

Genes are not the only things that can affect a complex trait. Often environmental factors can also be involved. The type of environmental factors can be very different for different traits. One obvious example of this is lung cancer. Smoking cigarettes greatly increases the risk of developing lung cancer. Smoking also seems to have an effect on other diseases, including some eye diseases (such as age-related macular degeneration). However, not every chronic smoker will develop lung cancer or...

Life Span and the Aging Process

How long an organism lives is called its life span. In 1998, the average life span for a human, worldwide, was sixty-six years. However, life span is a complex trait, meaning that many factors, including family history, lifestyle, disease, and residence in a developed nation, determine how long an individual's life will be. The average life span in a particular population changes as these factors change. For example, the average life span in the United States in 1900 was forty-nine in 1998 it...

Alcoholism in Humans

The techniques available for human research are more limited, and many questions remain. Although behavior geneticists now possess the techniques to identify genetic influence and to begin to identify specific genes, questions remain regarding which behaviors, actions, and activities of people are the best candidates for behavior-genetic study. Again, alcohol use and abuse provide an illustration. Alcoholism is a major social and medical problem in the United States and in most of the world. It...

Twin Studies of Alcoholism

That risk-related behaviors are evident early in life, remain stable into adolescence, and are associated with a family history of alcoholism suggests that those behaviors are, at least in part, of genetic origin. To establish that, researchers must use genetically informative study designs. One approach is to study child or adolescent twins and their parents. Several such studies, which specifically assess the initiation of alcohol use and the transition to alcohol abuse, are being conducted...

Heritability in Humans

Most family, twin, and adoption studies have shown that addiction to alcohol has significant heritability. For example, there is an increased risk for alcoholism in the relatives of alcoholics. Depending on the study, the risk of alcoholism in siblings of alcoholics is between 1.5 and 4 times the risk for the general population. The identical twins of alcoholics (who share 100 percent of their genes) are more likely to be alcoholics than the fraternal twins of alcoholics (who share only about...

Cancer Causing Chemicals

References to cancer have been found in the annals of human disease since ancient times, but the disease's association with carcinogen exposure is a relatively new concept. Sir Percival Potts, a British physician who lived in the eighteenth century, was the first to suggest that the induction of cancer might be linked to agents in the environment. Potts had observed high rates of scrotal and nasal cancer among England's chimney sweeps, men who were exposed to accumulated fireplace soot during...

Genetic Testing and Alzheimers Disease

DNA testing can be performed to determine whether an individual has a mutation in one of the causative genes and or whether he or she carries one or two copies of the APOEe4 susceptibility gene. Whether to test and which test to perform will depend on three conditions family history of dementia, age of onset of disease, and clinical status of the individual. If a person has dementia, the test result could be useful in determining that the cause of the dementia is a form of AD. If a person has...