Noninduced Mutagenic Agents

Environmental agents can influence the mutation rate not only by increasing it, but also by decreasing it. For example, antioxidants, which are found commonly in fruits and vegetables, are thought by many to protect against mutagens that are generated by normal cellular respiration. In addition to protective agents, however, many plants also contain deleterious mutagens known as carcinogens. Many chemical mutagens exist both naturally in the environment and as a result of human activity....

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Cerns have shifted to include the growing number of recognized inherited disorders. Screening for inherited disorders began in the early 1960s, with testing for phenylketonuria (PKU), a metabolic disease that causes severe mental deficiency. Since that time, developments such as the completion of the Human Genome Project (HGP) has resulted in an increase in the number of genetic screening tests available. Types of population screening for inherited disorders can include newborn screening and...

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With the caveat that the intent is not to improve the gene pool, but to prevent suffering. This may mean terminating a pregnancy in which the fetus has a very bleak prognosis, which people opposed to abortion might find unethical. Opponents to this view point out that letting nature take its course can be painful for the fetus and may endanger the life of the woman. The ethics of prenatal diagnosis becomes more complicated when the goal is not to prevent suffering, but to choose a child of a...

Nomenclature

Somes that are not sex-determining (not X or Y) Like any other field in science, genetics has its own language. However, genetics is also a multidisciplinary field that encompasses expertise, and hence terminology, from diverse areas of science, including molecular biol-bioinformatics use of ogy, statistics, clinical medicine, and, most recently, bioinformatics. Despite information technology all of the new and changing language in the field, two of the most frequently used terms in genetics...

Basic and Applied Research

A molecular biologist might investigate the genetic basis of a disease, analyzing the gene or genes suspected of causing the disease at the molecular level by using the biochemical technique of DNA sequencing. Genes code for proteins that is, a particular gene contains the molecular information for producing one particular protein. A gene is expressed through transcription messen- the process of transcription. The DNA of the gene is transcribed by a protein known as RNA polymerase. Some genes...

Public Health Approaches in Genetics

Disease-related genetic variants that have been characterized include those associated with rare diseases as well as those that increase susceptibility to released by one cell to influence another common chronic diseases such as cancer and heart disease. Risk for almost all human diseases results from the interactions between inherited gene variants and environmental factors, including chemical, physical, and infectious agents, as well as behavioral or nutritional factors. Thus it appears...

Inheritance Patterns and Linkage Studies

Complex disorders such as schizophrenia and bipolar disorder usually do not follow classic Mendelian inheritance patterns, but they can frequently mimic a pattern of autosomal dominance with reduced penetrance. Explanatory models for these complex disorders include multifactorial inheritance (multiple genes with nongenetic components) and epistasis (few genes acting jointly). But, since the mode of inheritance is unknown, a range of analytic methods must be used to study the genetic aspects of...

Polyploidy

In eukaryotic organisms, chromosomes come in sets. The somatic cells, called soma, usually have a diploid chromosome number, which in scientific notation is abbreviated as 2N. The diploid state contains two sets of chromosomes, one set of which has been contributed by each parent. A single set of chromosomes composes the haploid chromosome number, which is abbreviated as N. The haploid set is found in reproductive cells or gametes (also called the germplasm). In humans the diploid number is 46,...

Less Invasive Methods

An ultrasound scan bounces soundwaves off of the fetus to create an image. A scan is often performed after the sixteenth week of pregnancy, and the anatomy and size of the fetus is measured to see if it is growing and developing normally. The scan can often detect major structural problems, such as a malformed heart or spine. An unusual finding on an ultrasound scan can be a warning to investigate further. However, not all birth defects can be detected by ultrasound. An ultrasound is sometimes...

Gene Imprinting

Methylation can also function in the process of genomic imprinting, which is found in sexually reproducing species. During sexual reproduction, each parent contributes one allele for each gene to the offspring. Genomic imprinting is a difference in gene expression that depends on whether the gene allele originated from the mother or the father. This differential pattern of gene expression occurs as the result of differential methylation in the gene promoter. One example of an imprinted gene is...

Plant Genetic Engineer

Plant genetic engineer is a popular term that describes scientists working in any of several fields who manipulate DNA or organelles such as chloro-plasts and mitochondria in plant cells. The specific titles of such a scientist can include plant physiologist, plant pathologist, weed scientist, cell biologist, botanist, molecular biologist, plant geneticist, and biochemist. The typical career path is to earn a doctorate in any of these fields, and then to go to work in industry, for the...

Myotonic Muscular Dystrophy

Myotonic muscular dystrophy (DM, or dystrophia myotonica) is the most common adult-onset muscular dystrophy, having a frequency of one per twenty thousand persons in the general population. Myotonia, the delayed relaxation of a voluntary muscle after it is contracted, and muscle weakness are the hallmarks of the disorder. For example, a person with DM using a hammer will not immediately be able to release his grip on the handle when finished. It is an autosomal dominant disorder, but there is...

Topic Outline

Agricultural Biotechnology Biopesticides Bioremediation Biotechnology Conservation Biology Genetic Approaches Pharmacogenetics and Pharmacogenomics Public Health, Genetic Techniques in Escherichia coli (E. coli bacterium) Transgenic Organisms Ethical Issues Human Genome Project Inheritance Patterns Meiosis Agricultural Biotechnology Biopesticides Bioremediation Biotechnology Biotechnology and Genetic Engineering, History Biotechnology Ethical Issues Cloning Genes Cloning Organisms DNA Vaccines...

Molecular Interactions and Drug Effectiveness

Pharmacogenomics is a branch of pharmacogenetics, a science that deals with the heritable traits responsible for the individual differences in the ways people respond to drugs. It is remarkable, considering the myriad of medications we have today, how little we understand about how most of them actually work. There are many factors that influence the effectiveness of a particular drug, including how the drug enters the body's cells, how rapidly it is degraded by metabolic enzymes, and how it...

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Computer generated representation of the enzyme neuraminidase (ribbons and strings) with an inhibitor (ball and stick) in the active site, a cleft on the enzyme's surface. This tertiary structure is built up from the primary structure (amino acid structure) and secondary structure. The arrows represent the beta-pleated sheet, a type of secondary structure. To observe the mosaic of proteins in life is to observe nature in its finest array. The feathers of a bird and the silk of a spider's web...

DNA Methylation and Human Disease

Changes in DNA methylation patterns have been implicated in the development and progression of many types of cancers. Additionally, defects in DNA methylation have been associated with several genetic diseases, including ICF (Immunodeficiency, Centromere Instability, and Facial Anomalies), Rett, and Fragile X syndromes, all of which result in variable degrees of mental retardation. This common effect on neurological function may result from the fact that DNA methylation occurs at high levels in...

Fatal versus Nonfatal Conditions

In order to understand why some aneuploid conditions are fatal and others (such as those mentioned above) are not, one must understand the concept of gene dosage and its importance in development. A normal human possesses twenty-two pairs of autosomes and two sex chromosomes (XY in the case of males and XX in the case of females). Such an individual develops normally because there is a situation of genetic balance Each gene is present in the correct amount (or dose), such that its contribution...

Glossary

A the Greek letter alpha 3 the Greek letter beta y the Greek letter gamma A the Greek letter lambda a the Greek letter sigma E. coli the bacterium Escherichia coli -ase suffix indicating an enzyme acidic having the properties of an acid the opposite of basic acrosomal cap tip of sperm cell that contains digestive enzymes for penetrating the egg adenoma a tumor (cell mass) of gland cells aerobic with oxygen, or requiring it agar gel derived from algae agglutinate clump together aggregate stick...

Mendels Scientific Legacy

While neither Mendel nor anyone else in his day knew anything about chromosomes or genes, the laws of inheritance he discovered predicted exactly how genes behave on chromosomes during the reproductive process. Indeed, the factors he discovered are genes, which come in pairs and segregate on separate chromosomes during sperm and egg production, just as he suggested. Gene pairs located on different sets of chromosomes will assort independently during the process. While most genes do not exhibit...

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RNA Interference RNA Polymerases RNA Processing Signal Transduction Transcription Transcription Factors Translation Attention Deficit Hyperactivity Disorder Disease, Genetics of Down Syndrome Fragile X Syndrome Growth Disorders Hemoglobinopathies Hemophilia Human Disease Genes, Identification of GENETIC MEDICINE DIAGNOSIS, TESTING, AND TREATMENT Embryonic Stem Cells Epidemiologist Gene Discovery Gene Therapy Human Disease Genes, Identification of Pharmacogenetics and Pharmacogenomics Population...

Repairing the Damage

DNA is constantly being damaged, and it is constantly being repaired as well. It is only when the damage is not repaired that a mutation can lead to cancer or cell death. The DNA repair enzymes can recognize damaged nucleotides and remove and replace them. The human liver contains a large number of enzymes whose role is to detoxify toxic compounds, mutagenic or otherwise, by chemically reacting them. However, in some cases these enzymes (called cytochrome P450s) actually create mutagens during...

Sequencing Techniques

The most widely used technique for sequencing proteins is the Edman degradation, a procedure developed by Pehr Edman in the 1950s. The reaction steps used for this method have since been completely automated by machine. The procedure uses special reagents under alternating basic and acidic conditions to remove one amino acid at a time from the protein's N-terminus. As each amino acid is released during each cycle of degradation, it is identified by chromatography, a separation technique that...

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...

The Patent Process

Once the patent application is filed, the application is assigned to a patent examiner, who then has the responsibility of reviewing the application and determining whether the invention is entitled to patent protection. Often, the examiner initially rejects the claims that indicate what the inventor wants to protect. This occurs when the examiner finds these claims to be too broad or unfounded. This leads to a procedure known as the prosecution of the application, in which the examiner and the...

Treatment of the Muscular Dystrophies

As of mid-2002, gene therapy treatment of LGMD was tried in a very small number of patients. These early experiments delivered a functional gene to a very small muscle in the foot and were designed to test the long-term safety and effectiveness of the treatment. Gene therapy for DMD is much more problematic, because of the immense size of the gene and the distribution throughout the body that would be required for effective treatment. Drug treatment with prednisone or other corticosteroids is...

The Causes of Nondisjunction and Its Frequency in Humans

Meiosis is a very tightly regulated process, and a whole series of control mechanisms (constituting a number of checkpoints) exist to ensure that everything proceeds in the correct manner. If an error should occur during the process, it is usually corrected. Nondisjunction is the result of a mistake at the level of chromosome segregation, which involves the spindle fibers. In normal meiosis, there is a mechanism that monitors the correct formation of the spindle fibers, the correct attachment...

Tourettes Syndrome

Some psychiatric disorders, like Tourette's syndrome, have significant overlap (co-morbidity) with other psychiatric disorders (OCD and ADHD in the case of Tourette's). This may make the elucidation of genetic causes more difficult. Tourette's syndrome is characterized by multiple motor tics and one or more vocal tics. It has onset before eighteen years and is one and one-half to three times more common in males. Twin, adoption, and segregation analysis studies support a genetic etiology for...

Lysosomal Storage Disorders

Macromolecules large Lysosomes are intracellular compartments in which macromolecules are molecules such as proteins, carbohydrates, and nucleic acids broken down in an acidic environment. Various classes of lysosomal storage disorders arise when there are defects in specific enzymes, and the manifestations of these disorders depend upon the class of macromolecule whose breakdown is affected. Gaucher's Disease. The most common lysosomal storage disorder is Gaucher's disease, caused by a...

Contributors

Oregon State University Department of Genetics DNA Repair Laboratory Technician Molecular Biologist Andrea Bernasconi Cambridge University, U.K. Multiple Alleles Nondisjunction C. William Birky, Jr. University of Arizona Inheritance, Extranuclear Joanna Bloom New York University Medical Center Cell Cycle Deborah Blum University of Wisconsin, Madison Science Writer Bruce Blumberg University of California, Irvine Hormonal Regulation Suzanne Bradshaw University of Cincinnati Transgenic Animals...

Approaches to Treatment

Treatment approaches for metabolic disorders include (a) modifying the diet to limit the amount of a precursor that is not metabolized properly (b) using cofactors or vitamins to enhance the residual activity of a defective enzyme system (c) using detoxifying agents to provide alternative pathways for the removal of toxic intermediates (d) enzyme replacement, to provide functional enzymes exogenously (from the outside) (e) organ transplantation, which in principle allows for endogenous...

Viewing Chromosomes

Biologists first tried to visualize the chromosomes in a human cell in the late nineteenth century, with estimates of the total number ranging from 30 to 80. As methods to untangle and stain chromosomes improved, the count narrowed to 46 or 48, and by 1956 was confirmed as 46, or 23 pairs. By 1959, the first chromosomal abnormalities were identified using size and crude staining patterns to distinguish the chromosomes. In the 1970s, vastly cytogeneticists scien- improved staining techniques...

Schizophrenia and Bipolar Disorder

Schizophrenia is a disorder characterized by psychotic symptoms such as hallucinations, delusions, and disordered thinking, as well as deficits in emotional and social behavior. Numerous family, twin, and adoption studies have provided substantial evidence for genetic factors in the etiology of this dis- etiology causation of disease, or the study of causation order. Nongenetic factors also appear to play an important role. The risk for relatives of an individual with schizophrenia is 6.5...

Organelle Structure and Energy Production

The mitochondria singular mitochondrion are enclosed by two membranes, each a phospholipid bilayer with a unique collection of embedded proteins. The outer membrane is smooth, but the inner membrane contains extensive folds called cristae. The cristae provide a means of packing a relatively large amount of the inner membrane into a very small container, thus enhancing the productivity of cellular respiration. The number of mitochondria per cell is correlated with the cell's level of metabolic...