Genetics
Genetics
Genetic recombination and mutations
Genetics and the golden age of biology
Ethical questions and the future of genetics
Genetics is the branch of biology concerned with the science of heredity, or the transfer of specific characteristics from one generation to the next. Genetics, from the Greek genno (give birth), focuses primarily on genes, coded units found along the DNA (deoxyribonucleic) acid molecules of the chromosomes, housed by the cell nucleus. Together, genes make up
the blueprints that determine the entire development of the species of organisms down to specific traits, such as the color of eyes and hair.
DNA is a molecule of nucleic acid that contains the genetic code of a living thing, or the physical characteristics that are passed down to a child from parents. Its shape is similar to a ladder that has been twisted into the shape of a winding staircase—what scientists call a twisted double strand double helix. All living things that contain cells have DNA. In mammals, such as humans, the pieces of DNA are grouped into structures called chromosomes, which are located in cell nuclei. The genetic material that is needed for humans to develop and grow is contained in DNA. The hereditary characteristics that pass from one generation to the next are also contained in DNA. An example of a hereditary characteristic that is inherited from parent to child is the blonde hair of a son born to parents who both have blonde hair.
Geneticists are concerned with three primary areas of gene study: how genes are expressed and regulated in the cell, how genes are copied and passed on to successive generations, and what are the genetic basis for differences between the species. Although the science of genetics dates back at least to the nineteenth century, little was known about the exact biological makeup of genes until the 1940s. Since that time, genetics has moved to the forefront of biological research.
DNA was first sequenced in 1977 by the independent work of English biochemist Frederick Sanger (1918–) and American molecular biologists Walter Gilbert (1932–) and Allan M. Maxam. The first genome completely sequenced occurred in 1980 when bacteriophage φ-X174 (a particular virus that had infected a bacterium) was sequenced. In 1989, American physician-geneticist Francis S. Collins (1950–) and Chinese geneticist Lap-Chee Tsui (1950–) sequenced the first human gene.
In 1990, the Human Genome Project (HGP) began in the United States. It was a coordinated international scientific project to understand and map the human genome so that all of its genes were identified. Other countries participating in HGP included France, Germany, Japan, and the United Kingdom. HGP members identified about 20,000 to 25,000 genes in the nucleus of a human cell and mapped the location of these genes on the 23 pairs of human chromosomes.
The Human Genome Project and Celera Genomics simultaneously released an initial draft of the human genome in February 2001. The HGP completed the final sequencing of the human genome (with 99% of the genome sequenced to a 99.99% accuracy) in April 2003. The result will not only be a greater understanding of the human body, but provide new insights into the origins of disease and the formulation of possible treatments and cures.
The history of genetics
The study of heredity the science called genetics— started in the 1800s, when scientists first began trying to explain the existence of different species and variations within the same species. At that time, French biologist Jean Baptiste de Lamarck (1744–1829) strongly believed that acquired characteristics would improve when routinely used over time. Those characteristics that were not used simply faded away. Lamarck also maintained that acquired characteristics were inherited from one generation to the next. In other words, Lamarck believed that if a giraffe continuously stretched its neck to reach for food, it would develop a longer neck. Further, the longer neck would be passed on to the next giraffe generation. Although his belief that acquired characteristics were inherited was incorrect, Lamarck was on the right track. He implied that traits can be inherited from generation to generation—that species undergo long-term evolutionary changes.
In 1859, English naturalist Charles Darwin (1809-1882) published his landmark book The Origin of Species, in which he outlined his theory of evolution through natural selection. Darwin believed that members of a particular species have slightly different characteristics. In the competition for space, food, and shelter, some of these characteristics would make a particular plant or animal better able to survive and produce offspring than others of its species. Therefore, these advantageous characteristics would persist in future generations, while those less advantageous ones would disappear as their carriers died out. After centuries or millennia of competition or natural selection, recent members of a species might be quite different from their ancestors. This theory gained advocates like English physician Thomas Huxley (1825–1895), who, did more than anyone else to overcome opposition to Darwinian theory. But even with all the support, Darwin’s theory still lacked an explanation for how the differences in species occurred.
Although humans have known about inheritance for thousands of years, the first scientific evidence for the existence of genes came in 1866. At that time, Austrian monk and geneticist Gregor Johann Mendel (1822–1937) published the results of a study of hybridization of plants—the combining of two individual species with different genetic make-ups to produce a new individual. Working with pea plants with specific characteristics such as height (tall and short) and color (green and yellow), Mendel bred one type of plant for several successive generations. He found that certain characteristics appeared in the next generation in a regular pattern. From these observations, he deduced that the plants inherited a specific biological unit (which he called factors (now called alleles), genes determining different forms of a single characteristic) from each parent. Mendel also noted that when factors or alleles pair up, one is dominant (which means it determines the trait, like tallness) while the other is recessive (which means it has no bearing on the trait). It is now understood that alleles may be single genes or sets of genes working together, each contributing to the final form of a physical characteristic (multiple allelism).
In 1884, German biologist August Weissmann proposed that a special hereditary substance existed in the egg nucleus, which he termed germ plasm. His theories concerning the behavior of this substance— later identified as chromosomes—were eventually proved correct. However, he mistakenly believed that the germ plasm passed intact from generation to generation, unchanged by any environmental factors. Weissmann’s theory, therefore, could not adequately account for the changes that occurred between generations and drove Darwin’s theory of evolution.
The period of classical genetics, in which researchers had no knowledge of the chemical constituents in cells that determine heredity, lasted well into the twentieth century. However, several advances made during that time contributed to the growth of genetics. In the eighteenth century, scientists used the relatively new technology of the microscope to discover the existence of cells, the basic structures in all living organisms. By the middle of the nineteenth century, they had discovered that cells reproduce by dividing.
Although Mendel laid the foundation of genetics, his work began to take on true significance in 1903 when German biologist Theodor Henrich Boveri (1862–1915) and American geneticist Walter Stanborough Sutton (1877–1916) independently proposed a chromosomal theory of inheritance. They discovered that chromosomes during gamete production behave like the socalled Mendel’s particles behave. In 1910, American zoologist and geneticist Thomas Hunt Morgan (1866-1946) confirmed the existence of chromosomes through experiments with fruit flies. He also discovered a unique pair of chromosomes called the sex chromosomes, which determined the sex of offspring. Morgan deduced that specific genes reside on chromosomes from his observation that an X-shaped chromosome was always present in flies that had white eyes. A later discovery showed that chromosomes could mutate or change structurally, resulting in a change in characteristics which could be passed on to the next generation.
More than three decades passed before scientists began to delve into the specific molecular and chemical structures that make up chromosomes. In the 1940s, a research team led by Oswald Avery (1877–1955) discovered that deoxyribonucleic acid (DNA) was responsible for transformation of non-pathogenic bacteria into pathogenic ones. The final proof that DNA was the specific molecule that carries genetic information was made by Alfred Day Hershey (1908–1997) and Martha Cowles Chase (1927–2003) in 1952. They used radioactive label to differentiate between viral protein and DNA, proving that over 80% of viral DNA entered bacterial cell causing infection, while protein did not cause infection.
The most important discovery in genetics occurred in 1953, when American microbiologist James Watson (1928–) and English scientist Francis Crick (1916–2004) solved the mystery of the exact structure of DNA. The two scientists used chemical analyses and x-ray diffraction studies performed by other scientists to uncover the specific structure and chemical arrangement of DNA. X-ray diffraction is a procedure in which parallel x-ray beams are diffracted by atoms in patterns that reveal the atom’s atomic weight and spatial arrangement. A month after their double-helix model of DNA appeared in scientific journals, the two scientists showed how DNA replicated. Armed with these new discoveries, geneticists embarked on the modern era of genetics, including efforts like genetic engineering, gene therapy, and a massive project to determine the exact location and function of all of the 20,000 to 25,000 genes that make up the human genome.
The biology of genetics
Genetic information is contained in the chromosomes, threadlike structures composed of DNA, and present in the nuclei of all cell types and are passed to daughter cells during cell division. Multicellular organisms contain two types of cells—body cells (or somatic cells) and germ cells (or reproductive cells). Germ cells are the ones that pass on the genetic information to the progeny. In contrast to somatic cells that contain dual copies of chromosomes in each cell, germ cells replicate through a process called meiosis, which ensures that the germ cells have only a single set of chromosomes, a condition called haploidy (designated as n). The somatic cells of humans have 23 pairs of chromosomes (46 chromosomes overall), a condition known as diploid (or 2n). Through the process of meiosis, a new cell, called a haploid gamete, is created with only 23 chromosomes: this is either the sperm cell of the father or the egg cell of the mother. The fusion of egg and sperm restores the diploid chromosome number in the zygote. This cell carries all the genetic information needed to grow into an embryo and eventually a full-grown human with the specific traits and attributes passed on by the parents. Offspring of the same parents differ because the sperm cells and egg cells vary in their gene sequences, due to random recombination.
The somatic, or body cells are the primary components of functioning organisms. The genetic information in these cells is passed on through a process of cell division called mitosis. Unlike meiosis, mitosis is designed to transfer the identical number of chromosomes during cell regeneration or renewal. This is how cells grow and are replaced in exact replicas to form specific tissues and organs, such as muscles and nerves. Without mitosis, an organism’s cells would not regenerate, resulting not only in cell death, but possible death of the entire organism. (It is important to note that some organisms reproduce asexually by mitosis alone.)
The genetic code
To understand genes and their biological function in heredity, it is necessary to understand the chemical makeup and structure of DNA. Although some viruses carry their genetic information in the form of ribonucleic acid (RNA), most higher life forms carry genetic information in the form of DNA, the molecule that makes up chromosomes.
The complete DNA molecule is often referred to as the blueprint for life because it carries all the instructions, in the formation of genes, for the growth and functioning of most organisms. This fundamental molecule is similar in appearance to a spiral staircase, which is also called a double helix. The sides of the DNA double helix ladder are made up of alternate sugar and phosphate molecules, like links in a chain. The rungs, or steps, of DNA are made from a combination of four nitrogen-containing bases—two purines (adenine [A] and guanine [G]) and two pyria set of 64midines (cytosine [C] and thymine [T]). The four letters designating these bases (A, G, C, and T) are the alphabet of the genetic code. Each rung of the DNA molecule is contains a combination of two of these letters, one jutting out from each side. In this genetic code, A always combines with T, and C with G to make what is called a base pair. Specific sequences of these base pairs, which are bonded together by atoms of hydrogen, make up the genes.
While a four-letter alphabet may seem rather small for constructing the comprehensive vocabulary that describes and determines the myriad life forms on the Earth, the sequences or order of these base pairs are nearly limitless. For example, various sequences or rungs that make up a simple six base gene could be ATCGGC, TAATCG, AGCGTA, or ATTACG, and so on. Each one of these combinations has a different meaning. Different sequences provide the code not only for the type of organism, but also for specific traits like brown hair and blue eyes. The more complex an organism, from bacteria to humans, the more rungs or genetic sequences appear on the ladder. The entire genetic makeup of a human, for example, contains about three billion base pairs, with the average gene unit being a few thousand base pairs long. Except for identical twins, no two humans have exactly the same genetic information. About 98% of DNA in chromosomes carry no genetic information.
Genetic information is duplicated during the process of DNA replication, which begins a few hours before the initiation of cell division (mitosis). To produce identical genetic information during mitosis, the hydrogen bonds holding together the two halves of the DNA ladder unzip, in presence of proteins called helicases, to expose single strands of DNA. These old strands act as templates to make new DNA molecules. Replication is initiated by this separation of DNA, and requires short DNA fragments (primers) to start synthesis of a new DNA strand by specific cellular enzymes called DNA polymerases. DNA rarely mutates during replication, as the proofreading and repair enzymes make sure that any errors are quickly repaired to protect the accuracy of the genetic information. Once completed, each new half of the DNA ladder has the identical information as the old one. The fact that T always combines with A and C with G achieves this process, therefore if the template had a sequence ATGCTG the newly made second strand will be TACGAC. When cell mitosis is completed, each new cell contains an exact replica of the DNA.
Cells contain hundreds of different proteins and its functions are dependent on which of the thousands of types of different proteins it contains. Proteins are made up of chains of amino acids. The arrangement of the amino acids to build specific proteins is determined by the base pair sequence contained or encoded in DNA. This genetic information has to be converted to proteins building over half of all solid body tissues and control most biological processes within and among these tissues. This is achieved by using the genetic code, which is a set of 64 (or, 43) triplets of bases (called codons) corresponding to each amino acid and the initiation and termination signals for protein synthesis.
As the sites of protein production lie outside the cell nucleus, the instructions for making them have to be transported out of the nucleus. The messenger that carries these instructions is messenger RNA, or mRNA (a single stranded molecule that has a mirror image of the base pairs on the DNA). The mRNA is made in the nucleus during a process called transcription and a single molecule of RNA carries instructions for making only one protein. After being exported out of the nucleus it is transported to ribosomes, which are the protein factories in the cell. In ribosomes the information from mRNA is decoded to produce a protein. This process is called translation. The flow of information is only one way from DNA to RNA and to protein. Therefore, characteristics acquired during an organism’s life, such as larger muscles or the ability to play the piano, cannot be inherited. However, people may have genes that make it easier for them to acquire these traits through exercise or practice.
Dominant and recessive traits
The expression of the products of genes is not equal, and some genes will override others in expressing themselves as an inherited characteristic. The offspring of organisms that reproduce sexually contain a set of chromosome pairs, half from the father, and half from the mother. However, normally people do not have one blue eye and one brown eye, or half brown hair and half blond hair because most genetic traits are the result of the expression of either the dominant or the recessive genes. If a dominant and a recessive gene appear together (the heterozygous condition), the dominant will always win, producing the trait for which it is coded. The only time a recessive trait (such as the one for blond hair) expresses itself is when two recessive genes are present (the homozygous condition). As a result, parents with heterozygous genes for brown hair could produce a child with blond hair if the child inherits two recessive blondhair genes from the parents. The genes residing in the chromosome’s DNA can also be present in alternative forms called alleles. It is important to note that some characteristics are a result of presence of various alleles, e.g. pink snapdragon flowers or blood types.
This hereditary law also holds true for genetic diseases. Neither parent may show signs of a genetic disease, caused by a defective gene, but they can pass the double-recessive combination on to their children. Some genetic diseases are dominant and others are recessive. Dominant genetic defects are more common because it only takes one parent to pass on a defective allele. A recessive genetic defect requires both parents to pass on the recessive allele that causes the disease. A few inherited diseases (such as Down syndrome) are caused by abnormalities in the number of chromosomes, where the offspring has 47 chromosomes instead of the normal 46.
Genetic recombination and mutations
The DNA molecule is extremely stable, ensuring that offspring have the same traits and attributes that will enable them to survive as well as their parents. However, a certain amount of genetic variation is necessary if species are to adapt by natural selection to a changing environment. Often, this change in genetic material occurs when chromosome segments from the parents physically exchange segments with each other during the process of meiosis. This is known as cross over or intrinsic recombination.
Genes can also change by mutations on the DNA molecule, which occur when a mutagen alters the chemical or physical makeup of DNA. Mutagens include ultraviolet light and certain chemicals. Genetic mutations in somatic (body) cells result in malfunctioning cells or a mutant organism. These mutations result from a change in the base pairs on the DNA, which can alter cell functions and even give rise to different traits. Somatic cell mutations can result in disfigurement, disease, and other biological problems within an organism. These mutations occur solely within the affected individual.
When mutations occur in the DNA of germ (reproductive) cells, these altered genes can be passed on to the next generation. A germ cell mutation can be harmful or result in an improvement, such as a change in body coloring that acts as camouflage. If the trait improves an individual organism’s chances for survival within a particular environment, it is more likely to become a permanent trait of the species because the offspring with this gene would have a greater chance to survive and pass on the trait to succeeding generations.
Mutations are generally classified into two groups, spontaneous mutations and induced mutations. Spontaneous mutations occur naturally from errors in coding during DNA replication. Induced mutations come from outside influences called environmental factors. For example, certain forms of radiation can damage DNA and cause mutations. A common example of this type of mutating agent is the ultraviolet rays of the Sun, which can cause skin cancer in some people who are exposed to intense sunlight over long periods of time. Other mutations can occur due to exposure to artificially made chemicals. These types of mutations modify or change the chemical structure of base pairs.
Population genetics
Population genetics is the branch of genetics that focuses on the occurrence and interactions of genes in specific populations of organisms. One of its primary concerns is evolution, or how genes change from one generation to the next. By using mathematical calculations that involve an interbreeding population’s gene pool (the total genetic information present in the individuals within the species), population geneticists delve into why similar species vary among different populations that may, for example, be separated by physical boundaries such as bodies of water or mountains.
As outlined in the previous section, genetic mutations may cause changes in a population if the mutation occurs in the germ cells. Many scientists consider mutation to be the primary cause of genetic change in successive generations. However, population geneticists also study three other factors involved in genetic change or evolution: migration, genetic drift, and natural selection.
Migration occurs when individuals within a species move from one population to another, carrying their genetic makeup with them. Genetic drift is a natural mechanism for genetic change in which specific genetic traits coded in alleles (alternate states of functioning for the same gene) may change by chance often in a situation where organisms are isolated, as on an island.
Natural selection, a theory first proposed by Charles Darwin in 1858, is a process that occurs over successive generations. The theory states that genetic changes that enhance survival for a species will come to the forefront over successive generations because the gene carriers are better fit to survive and are more likely reproduce, thus establishing a new gene pool, and eventually, perhaps, an entirely new species. One proposed mechanism of natural selection is gradualism, which predicts very slow and steady accumulation of beneficial genes. Punctuated equilibrium, in contrast, depicts natural selection as occurring in brief, but accelerated periods of survival of the fittest with lengthy periods of relative stagnation of genetic change in populations. Some scientists hold that both processes occur and have occurred.
Genetics and the golden age of biology
More than any other biological discipline, genetics is responsible for the most dramatic breakthroughs in biology and medicine today. Scientists are rapidly advancing in their ability to engineer genetic material to achieve specific characteristics in plants and animals. The primary way to genetically engineer DNA is called gene cloning, in which a segment of one DNA molecule is removed and then inserted, into another DNA molecule. This process takes advantage of restriction enzymes to cut DNA into fragments of different lengths and ligase to re-create new molecules. Restriction enzymes act as molecular scissors, cutting larger molecules (like DNA) at specific sites. The ends of these fragments are sticky in that they have an affinity for complimentary ends of other DNA fragments. DNA ligase acts as a glue to join the ends of the two molecules together. This approach has applications in agriculture and medicine.
In agriculture, genetic engineering is used to produce transgenic animals or plants, in which genes are transferred from one organism to another. This approach has been used to reduce the amount of fat in cattle raised for meat, or to increase proteins in the milk of dairy cattle that favor cheese making. Fruits and vegetables have also been genetically engineered so they do not bruise as easily, or so they have a longer shelf life at the grocery store. On the other hand, in medicine, genetic engineering provided great advancements in production of antibiotics, hormones, and vaccines, understanding disease mechanisms and in therapy. Gene therapy is currently being developed and used as it provides the opportunity to introduce specific genes into the body to correct a genetic defect or to enhance the body’s capabilities to fight off disease and repair itself. Because many inherited or genetic diseases are caused by the lack of an enzyme or protein, scientists hope to one day treat the unborn by inserting genes to provide the missing enzyme.
Genetic fingerprinting (DNA typing) is based on each individual’s unique genetic code. To identify parentage, diagnose inherited diseases in prenatal laboratories or the presence of someone at a crime, scientists use molecular biology techniques such as DNA fingerprinting by applying restriction fragment length polymorphisms (RFLPs) analysis (identifying the characteristic patterns in DNA cut with the restriction enzymes), microsattelite analysis (looking at the small specific DNA sequences), DNA hybridization, DNA sequencing or polymerase chain reaction (PCR). Development of PCR provides the ability to analyze small amounts of DNA acquired from hair, semen, blood, fingernail fragments, or fetal cells by utilizing DNA polymerase enzyme (the same enzyme used naturally by cells in mitosis) to create identical copies of a DNA molecules from small samples.
One of the most exciting recent developments in genetics is the completion of the Human Genome Project (HGP). This project provided a complete genetic road map outlining the location and function of the 20,000 to 25,000 genes found in human cells encoded in about three billion bases. The first human genome draft sequences were published in February 2001 by the Celera company and the HGP consortium in the journals Science and Nature, respectively. Due to technological advances and huge international cooperation throughout the project, the essentially complete genome was finished on April 14, 2003, a full five years ahead of schedule, with 99% of the genome sequenced at 99.9% accuracy. Then, in May 2006, the last chromosome sequence was published in the journal Nature As a result, genetic researchers will have easy access to specific genes to study how the human body works and to develop therapies for diseases. Gene maps for other species of animals are also being developed.
Future of genetics
Full sequencing of many bacterial genomes, yeast, Caenorhabditis elegans, Drosophila, mouse, and human genomes has brought about a new era in genetics, and a development of a new area—genomics, or the study of the sequences of genes within living things. Sequencing means that the structure of deox-yribonucleic acid (DNA) from a particular living thing is discovered—what scientists called mapped. Specifically, genomic scientists identify and analyze the structure of genes within segments of DNA. Inside any organism, the complete set of chromosomes—or all the genetic information contained in genes—is called its genome. The set of chromosomes inside people is called the human genome. Availability of full DNA sequences of multiple organisms allows the comparative analysis (comparative genetics) of genomes allowing gene identification, finding of regulatory sequences and tracing evolution.
Genetic analysis proved very successful in Mendelian diseases. New challenges for genetics are the studies of common complex diseases such as asthma, obesity and hypertension. These diseases are caused by interaction of multiple genes and the
KEY TERMS
Allele— Any of two or more alternative forms of a gene that occupy the same location on a chromosome.
Amino acid— An organic compound whose molecules contain both an amino group (-NH2) and a carboxyl group (-COOH). One of the building blocks of a protein.
Base — A chemical unit that makes up part of the DNA molecule. There are four bases: adenine (A) and guanine (G), which are purines, and cytosine (C) and thymine (T), which are pyrimidines.
Chromosomes— The structures that carry genetic information in the form of DNA. Chromosomes are located within every cell and are responsible for directing the development and functioning of all the cells in the body.
DNA— Deoxyribonucleic acid; the genetic material in a cell. Chromosomes are made of DNA.
Dominant (dominant gene)— An allele of a gene that results in a visible phenotype if expressed in a heterozygote.
Gene— A discrete unit of inheritance, represented by a portion of DNA located on a chromosome. The gene is a code for the production of a specific kind of protein or RNA molecule, and therefore for a specific inherited characteristic.
Genetic recombination— New configurations produced when two DNA molecules are broken and rejoined together during meiosis.
Heredity— Characteristics passed on from parents to offspring.
Heterozygous— Two different forms of the same allele pair on the chromosome.
Homozygous— Two identical forms of the same allele pair on the chromosome.
Meiosis— The process of cell division in germ or reproductive cells, producing haploid genetic material.
Mitosis— The process of cell division in somatic, or body, cells, producing no change in genetic material.
Proteins— Macromolecules made up of long sequences of amino acids. They make up the dry weight of most cells and are involved in structures, hormones, and enzymes in muscle contraction, immunological response, and many other essential life functions.
Recessive— Refers to the state or genetic trait that only can express itself when two genes, one from both parents, are present and coded for the trait, but will not express itself when paired with a dominant gene. (See Dominant; Allele)
Ribonucleic acid— RNA; the molecule translated from DNA in the nucleus that directs protein synthesis in the cytoplasm; it is also the genetic material of many viruses.
Transcription— The process of synthesizing RNA from DNA
environment, making their analysis even more difficult. Geneticists analyze DNA sequence to correlate any changes with the disease (association studies). Small fragments of repetitive DNA sequence (microsattelites) or single nucleotide polymorphisms (SNPs) are analyzed. Such studies require analysis of large control (healthy) population in addition to the affected group before any conclusions can be made. Solving of the puzzle of complex traits is going to be possible by combining molecular genetics, biostatis-tics, further clinical and computational/bioinformati-cal analysis.
Ethical questions and the future of genetics
Despite the promise of genetics research, many ethical and philosophical questions arise. Many of the concerns about this area of research focus on the increasing ability to manipulate genes. There is a fear that the results will not always be beneficial. For example, some fear that a genetically re-engineered virus could turn out to be extremely virulent, or deadly, and may spread if there is no way to stop it.
Another area of concern is the genetic engineering of human traits and qualities. Altering genetic material, for example, will let doctors diagnose and treat many diseases and help scientists improve the safety of foods. It will also give scientists the ability to change the physical and psychological traits of people. If a woman has an inherited heart problem, doctors could alter her genetic material so babies born to her in the future will not have this problem. The goal is to produce people with specific traits such as better health, improved looks, or even high intelligence. While these traits may seem to be desirable on the surface, the concern arises about who will decide exactly what traits are to be engineered into human offspring, and whether everyone will have equal access to an expensive technology. Scientists could also alter such minor physical characteristics as hair color and height. Many people do not think it is ethical to change such traits by altering genetic materials. Some fear that the result could be domination by a particular socio-economic group.
Genetic information involves the gathering and storing of materials related to a person’s DNA. Issues have been raised as to what type of rules should be set up for the gathering and storing of such DNA information. Questions are being asked such as: How should that information be used? Who should be told? Who should be in charge of storing the information? Questions about personal privacy and other ethical considerations concerning genetic information have yet to be determined. Lawmakers, health insurance companies, medical organizations, and United States citizens will all take a part in answering these sensitive questions. As the scientific capabilities increase within genetic engineering, more genetic information will become available. Humans will—no doubt—face more difficult ethical and privacy questions about genomics in the future.
Despite these fears and concerns, genetic research continues. In an effort to ensure that the science is not abused in ways harmful to society, governments in the United States and abroad have created panels and organizations to oversee genetic research. For the most part, international committees composed of scientists and ethical experts state that the benefits of genetic research for medicine and agriculture far outweigh the possible abuses.
See also Chromosomal abnormalities; Gene splicing.
Resources
BOOKS
Carlson, Elof Axel. Mendel’s Legacy: The Origin of Classical Genetics. Cold Spring Harbor, NY: Cold Spring Harbor Laboratory Press, 2004.
Hartl, Danial, and Elizabeth Jones. Genetics: Analysis of Genes and Genomes. Sudbury, MA: Jones and Bartlett Publishers, 2005.
King, Robert C., William D. Stansfield, and Pamela K. Mulligan. A Dictionary of Genetics. New York: Oxford University Press, 2006.
Lewin, Benjamin. Essential Genes. Upper Saddle River, NJ: Pearson Education, 2006.
Lewis, Ricki. Human Genetics: Concepts and Applications. Boston, MA: McGraw-Hill, 2005.
PERIODICALS
Brookes, Anthony. “Rethinking Genetic Strategies to Study Complex Diseases.” Trends in Molecular Medicine (November 2001):512–6.
Guo, Sun-Wei, and Kenneth Lange, “Genetic Mapping of Complex Traits: Promises, Problems, and Prospects.” Theoretical Population Biology (February 2000):1–11.
Philips, Tamara J., and John K. Belknap, “Complex-trait Genetics: Emergence of Multivariate Strategies.” Nature Reviews. Neuroscience (June 2002):478–485
OTHER
National Institutes of Health. “Guide to the Human Genome.” <http://www.ncbi.nlm.nih.gov/genome/guide/human/> (accessed October 11, 2006).
David Petechuk