Gene Mutation

What are proteins and what do they do?
Proteins are large, complex molecules that play many critical roles in the body. They do most of the work in cells and are required for the structure, function, and regulation of the body’s tissues and organs.
Proteins are made up of hundreds or thousands of smaller units called amino acids, which are attached to one another in long chains. There are 20 different types of amino acids that can be combined to make a protein. The sequence of amino acids determines each protein’s unique 3-dimensional structure and its specific function.
Proteins can be described according to their large range of functions in the body, listed in alphabetical order:
Examples of protein functions
Function Description Example
Antibody Antibodies bind to specific foreign particles, such as viruses and bacteria, to help protect the body. Immunoglobulin G (IgG) (illustration)

Enzyme Enzymes carry out almost all of the thousands of chemical reactions that take place in cells. They also assist with the formation of new molecules by reading the genetic information stored in DNA. Phenylalanine hydroxylase (illustration)

Messenger Messenger proteins, such as some types of hormones, transmit signals to coordinate biological processes between different cells, tissues, and organs. Growth hormone (illustration)

Structural component These proteins provide structure and support for cells. On a larger scale, they also allow the body to move. Actin (illustration)

Transport/storage These proteins bind and carry atoms and small molecules within cells and throughout the body. Ferritin (illustration)

For more information about proteins and their functions:
A discussion of the role of proteins can be found in the NCBI Science Primer in the chapter called What Is A Genome? . Scroll down to the heading “Proteins.”
The Wellcome Trust provides basic information about protein structure and function .
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How do genes direct the production of proteins?
Most genes contain the information needed to make functional molecules called proteins. (A few genes produce other molecules that help the cell assemble proteins.) The journey from gene to protein is complex and tightly controlled within each cell. It consists of two major steps: transcription and translation. Together, transcription and translation are known as gene expression.
During the process of transcription, the information stored in a gene’s DNA is transferred to a similar molecule called RNA (ribonucleic acid) in the cell nucleus. Both RNA and DNA are made up of a chain of nucleotide bases, but they have slightly different chemical properties. The type of RNA that contains the information for making a protein is called messenger RNA (mRNA) because it carries the information, or message, from the DNA out of the nucleus into the cytoplasm.
Translation, the second step in getting from a gene to a protein, takes place in the cytoplasm. The mRNA interacts with a specialized complex called a ribosome, which “reads” the sequence of mRNA bases. Each sequence of three bases, called a codon, usually codes for one particular amino acid. (Amino acids are the building blocks of proteins.) A type of RNA called transfer RNA (tRNA) assembles the protein, one amino acid at a time. Protein assembly continues until the ribosome encounters a “stop” codon (a sequence of three bases that does not code for an amino acid).
The flow of information from DNA to RNA to proteins is one of the fundamental principles of molecular biology. It is so important that it is sometimes called the “central dogma.”



Through the processes of transcription and translation, information from genes is used to make proteins.
For more information about making proteins:
The Wellcome Trust provides a brief overview of gene expression .
The Genetic Science Learning Center at the University of Utah offers an interactive introduction to transcription and translation .
For a more detailed description of transcription and translation, refer to the NCBI Science Primer’s chapter titled What Is A Genome? . Scroll down to the heading “From Genes to Proteins: Start to Finish.”
The New Genetics, a publication of the National Institute of General Medical Sciences, includes discussions of transcription and translation .
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Can genes be turned on and off in cells?
Each cell expresses, or turns on, only a fraction of its genes. The rest of the genes are repressed, or turned off. The process of turning genes on and off is known as gene regulation. Gene regulation is an important part of normal development. Genes are turned on and off in different patterns during development to make a brain cell look and act different from a liver cell or a muscle cell, for example. Gene regulation also allows cells to react quickly to changes in their environments. Although we know that the regulation of genes is critical for life, this complex process is not yet fully understood.
Gene regulation can occur at any point during gene expression, but most commonly occurs at the level of transcription (when the information in a gene’s DNA is transferred to mRNA). Signals from the environment or from other cells activate proteins called transcription factors. These proteins bind to regulatory regions of a gene and increase or decrease the level of transcription. By controlling the level of transcription, this process can determine the amount of protein product that is made by a gene at any given time.
For more information about gene regulation:
More information about gene regulation can be found in the NCBI Science Primer. Refer to the chapter called What Is A Genome? and scroll down to the headings “Gene Switching: Turning Genes On and Off,” “Controlling Transcription,” and “Controlling Translation.”
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How do cells divide?
There are two types of cell division: mitosis and meiosis. Most of the time when people refer to “cell division,” they mean mitosis, the process of making new body cells. Meiosis is the type of cell division that creates egg and sperm cells.
Mitosis is a fundamental process for life. During mitosis, a cell duplicates all of its contents, including its chromosomes, and splits to form two identical daughter cells. Because this process is so critical, the steps of mitosis are carefully controlled by a number of genes. When mitosis is not regulated correctly, health problems such as cancer can result.
The other type of cell division, meiosis, ensures that humans have the same number of chromosomes in each generation. It is a two-step process that reduces the chromosome number by half—from 46 to 23—to form sperm and egg cells. When the sperm and egg cells unite at conception, each contributes 23 chromosomes so the resulting embryo will have the usual 46. Meiosis also allows genetic variation through a process of DNA shuffling while the cells are dividing.


Mitosis and meiosis, the two types of cell division.For more information about cell division:
For a detailed summary of mitosis and meiosis, please refer to the chapter titled What Is A Cell? In the NCBI Science Primer. Scroll down to the heading “Making New Cells and Cell Types.”
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How do genes control the growth and division of cells?
A variety of genes are involved in the control of cell growth and division. The cell cycle is the cell’s way of replicating itself in an organized, step-by-step fashion. Tight regulation of this process ensures that a dividing cell’s DNA is copied properly, any errors in the DNA are repaired, and each daughter cell receives a full set of chromosomes. The cycle has checkpoints (also called restriction points), which allow certain genes to check for mistakes and halt the cycle for repairs if something goes wrong.
If a cell has an error in its DNA that cannot be repaired, it may undergo programmed cell death (apoptosis) (illustration). Apoptosis is a common process throughout life that helps the body get rid of cells it doesn’t need. Cells that undergo apoptosis break apart and are recycled by a type of white blood cell called a macrophage (illustration). Apoptosis protects the body by removing genetically damaged cells that could lead to cancer, and it plays an important role in the development of the embryo and the maintenance of adult tissues.
Cancer results from a disruption of the normal regulation of the cell cycle. When the cycle proceeds without control, cells can divide without order and accumulate genetic defects that can lead to a cancerous tumor (illustration).
For more information about cell growth and division:
The National Institutes of Health’s Apoptosis Interest Group provides an introduction to programmed cell death.
The National Cancer Institute offers several publications that explain the growth of cancerous tumors. These include What You Need To Know About Cancer—An Overview and Understanding Cancer .
The Wellcome Trust offers brief overviews of the role of genes in cancer and the types of genes involved in cancer .
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How do geneticists indicate the location of a gene?
Geneticists use maps to describe the location of a particular gene on a chromosome. One type of map uses the cytogenetic location to describe a gene’s position. The cytogenetic location is based on a distinctive pattern of bands created when chromosomes are stained with certain chemicals. Another type of map uses the molecular location, a precise description of a gene’s position on a chromosome. The molecular location is based on the sequence of DNA building blocks (base pairs) that make up the chromosome.
Cytogenetic location
Geneticists use a standardized way of describing a gene’s cytogenetic location. In most cases, the location describes the position of a particular band on a stained chromosome:
17q12
It can also be written as a range of bands, if less is known about the exact location:
17q12-q21
The combination of numbers and letters provide a gene’s “address” on a chromosome. This address is made up of several parts:
• The chromosome on which the gene can be found. The first number or letter used to describe a gene’s location represents the chromosome. Chromosomes 1 through 22 (the autosomes) are designated by their chromosome number. The sex chromosomes are designated by X or Y.
• The arm of the chromosome. Each chromosome is divided into two sections (arms) based on the location of a narrowing (constriction) called the centromere. By convention, the shorter arm is called p, and the longer arm is called q. The chromosome arm is the second part of the gene’s address. For example, 5q is the long arm of chromosome 5, and Xp is the short arm of the X chromosome.
• The position of the gene on the p or q arm. The position of a gene is based on a distinctive pattern of light and dark bands that appear when the chromosome is stained in a certain way. The position is usually designated by two digits (representing a region and a band), which are sometimes followed by a decimal point and one or more additional digits (representing sub-bands within a light or dark area). The number indicating the gene position increases with distance from the centromere. For example: 14q21 represents position 21 on the long arm of chromosome 14. 14q21 is closer to the centromere than 14q22.
Sometimes, the abbreviations “cen” or “ter” are also used to describe a gene’s cytogenetic location. “Cen” indicates that the gene is very close to the centromere. For example, 16pcen refers to the short arm of chromosome 16 near the centromere. “Ter” stands for terminus, which indicates that the gene is very close to the end of the p or q arm. For example, 14qter refers to the tip of the long arm of chromosome 14. (“Tel” is also sometimes used to describe a gene’s location. “Tel” stands for telomeres, which are at the ends of each chromosome. The abbreviations “tel” and “ter” refer to the same location.)

The CFTR gene is located on the long arm of chromosome 7 at position 7q31.2.
Molecular location
The Human Genome Project, an international research effort completed in 2003, determined the sequence of base pairs for each human chromosome. This sequence information allows researchers to provide a more specific address than the cytogenetic location for many genes. A gene’s molecular address pinpoints the location of that gene in terms of base pairs. For example, the molecular location of the APOE gene on chromosome 19 begins with base pair 50,100,901 and ends with base pair 50,104,488. This range describes the gene’s precise position on chromosome 19 and indicates the size of the gene (3,588 base pairs). Knowing a gene’s molecular location also allows researchers to determine exactly how far the gene is from other genes on the same chromosome.
Different groups of researchers often present slightly different values for a gene’s molecular location. Researchers interpret the sequence of the human genome using a variety of methods, which can result in small differences in a gene’s molecular address. For example, the National Center for Biotechnology Information (NCBI) identifies the molecular location of the APOE gene as base pair 50,100,901 to base pair 50,104,488 on chromosome 19. The Ensembl database identifies the location of this gene as base pair 50,100,879 to base pair 50,104,489 on chromosome 19. Neither of these addresses is incorrect; they represent different interpretations of the same data. For consistency, Genetics Home Reference presents data from NCBI for the molecular location of genes.
For more information on genetic mapping:
The National Human Genome Research Institute explains how researchers create a genetic map .
The University of Washington provides a Cytogenetics Gallery that includes a description of chromosome banding patterns .
The NCBI Science Primer offers additional detailed information about genome mapping .
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What are gene families?
A gene family is a group of genes that share important characteristics. In many cases, genes in a family share a similar sequence of DNA building blocks (nucleotides). These genes provide instructions for making products (such as proteins) that have a similar structure or function. In other cases, dissimilar genes are grouped together in a family because proteins produced from these genes work together as a unit or participate in the same process.
Classifying individual genes into families helps researchers describe how genes are related to each other. Researchers can use gene families to predict the function of newly identified genes based on their similarity to known genes. Similarities among genes in a family can also be used to predict where and when a specific gene is active (expressed). Additionally, gene families may provide clues for identifying genes that are involved in particular diseases.
Sometimes not enough is known about a gene to assign it to an established family. In other cases, genes may fit into more than one family. No formal guidelines define the criteria for grouping genes together. Classification systems for genes continue to evolve as scientists learn more about the structure and function of genes and the relationships between them.
For more information about gene families
Genetics Home Reference provides information about gene families including a brief description of each gene family and a list of the genes included in the family.
The HUGO Gene Nomenclature Committee (HGNC) has classified many human genes into families. Each grouping is given a name and symbol, and contains a table of the genes in that family.
The textbook Human Molecular Genetics (second edition, 1999) provides background information on human gene families .
The Gene Ontology database lists the protein products of genes by their location within the cell (cellular component), biological process, and molecular function.
The Reactome database classifies the protein products of genes based on their participation in specific biological pathways. For example, this resource provides tables of genes involved in controlled cell death (apoptosis), cell division, and DNA repair

Information Technology

Current trends in information technology
Education field:
Computers and Internet connections are becoming widely available in schools and classrooms. In 1999, 99 percent of teachers in the United States had access to a computer in their schools, and 84 percent had one or more computers in their classrooms. At the same time, Internet connections were also widespread, with 95 percent of schools and 63 percent of classrooms having access. Worldwide, many countries are making the creation and diffusion of information and communications technology (ICT) an important priority. Even in developing countries, usage is increasing dramatically. As ICT becomes more widely available, teachers and policymakers are turning their attention to the difficult task of understanding how best to integrate this technology into learning environments.
ICT can be used in many different ways, and how it is integrated into educational settings depends largely on teachers' instructional goals and strategies. Changes in the goals of education during the latter part of the twentieth century, coupled with increases in the amount and type of available technology, has created changes in teachers' use of technology. In the 1970s and early 1980s the primary goal of instruction was to have students memorize important information and procedures. Instruction was teacher-led and dominated by lectures, followed by practice using worksheets and short-answer tests. Students worked alone to complete assignments, and when help was needed they consulted parents, teachers, or textbooks for assistance. If computers were available in classrooms during this time period, their use mirrored this dominant mode of instruction; that is, they were primarily used to present passages of text and test students' comprehension and memory for information contained in the passages.
Research on learning has demonstrated the shortcomings of this type of instruction. Students often forget memorized information, or they fail to apply it in situations where it would be useful. They need help in connecting new information to what they already know and in extending and applying their knowledge to new problems. Researchers in the early twenty-first century believe that students learn best when they work to combine their own past experience with new information in order to solve problems that are personally meaningful to them.
In addition to changes in the understanding of how students learn, there have been substantial changes in what educators and policymakers believe students should know how to do. The exponential growth in information since 1950 has shifted the purpose of education. Information has become abundant and easily accessible. Rather than reading the unified perspective typically presented by a textbook, students have access to many different points of view. Instead of memorizing, students now need assistance in learning how to find and select relevant information for problems they need to solve. They need to learn how to collaborate with others as they solve these problems and communicate their solutions to their teachers and to the world beyond their classroom.
Along with changes in what students should know and an increased understanding of how they learn, new approaches to instruction are being advocated. Instead of listening to lectures and memorizing facts and procedures, educational reforms suggest that students learn best in the context of solving complex, realistic problems. Traditional computer-assisted instruction (CAI) and many integrated learning systems (ILSs) deliver precisely this form of instruction in a range of subject-matter areas. Typically computers dedicated to ILSs are clustered in computer laboratory settings, rather than being located in individual teacher's classrooms. Students who acquire new information as they solve problems are able to understand its usefulness, remember it, and use it to solve problems in the future. Solving interesting problems is more likely to stimulate a student's interest than memorizing isolated facts, and this interest has been shown to positively affect learning. Students solving real problems view their efforts as real work and have a sense of purpose and value.
Organizing instruction around problem solving makes new demands on teachers, including locating meaningful problems and projects and providing students with the resources and guidance for solving them. Teachers are finding that ICT can help them meet these demands, and they are integrating it into their instruction in many new and exciting ways.
Technology and New Forms of Instruction
Using technology to find and represent educational problems. One major challenge for teachers interested in problem-based learning is locating problems that are appropriate for their students and for the topics that they need to learn. Problems must be complex enough to support sustained exploration and encourage collaboration, and they should have multiple interrelated parts to develop students' ability to break problems down and organize their solutions. Representing and communicating such complex problem situations is an important function of technology. Unlike problems that occur in the real world, technology can incorporate graphics, video, animation, and other tools to create problems that can be explored repeatedly. Multimedia representations are easier to understand than problems presented as text. One example of using technology to present problems is the mathematical problem-solving series, The Adventures of Jasper Woodbury. Each problem in the Jasper series is presented as a video story that ends when the main character experiences a problem that can be solved using math. Using technology that can be easily searched and paused for inspection, students search the video looking for clues to help them understand and solve the problem. In one episode, students explore a variety of transportation methods and routes to rescue a wounded bald eagle. They compare their solution plans and develop ways to determine which plan is best.
Microworlds are another type of technology used to present problems. One example is Thinkertools, a computer-based learning environment that simulates aspects of Newtonian physics. Using the Thinkertools microworld, students can manipulate various aspects of the environment, observe the results, and attempt to discover the rules that govern this simulation.
Internet and videoconferencing technology allow students to participate in projects sponsored by researchers around the world. In the Jason Project, satellite and Internet technology bring classroom students into direct real-time contact with leading scientists, conducting scientific research expeditions around the globe. Each year the project explores a different location in order to help students understand the earth's biological and geological development. Some of the past expeditions have studied deep-sea archaeology, compared shallow and deep ocean habitats, studied plate tectonics and volcanoes, and compared conditions experienced in space and under the oceans. In addition to observing research activities, students are able to ask questions and get immediate answers from the scientists.
Whatever type of technology is used, an important goal is to create problem representations that are interactive and under the learner's control. The student creates a plan for investigating the problem, and the technology creates an environment that makes flexible exploration possible.
Using technology to find educational resources. A second function of technology in problem-based learning environments is locating information needed to solve problems or do other kinds of research. In the past, teachers attempting a problem-based curriculum felt the need to limit problems to those for which they had expertise or the local library had resources. Now the World Wide Web brings a seemingly endless amount of information on almost any subject, and it is possible for students to choose topics based on personal interest rather than availability of resources.
Internet research projects are gaining rapidly in popularity. In the spring of 1998, 30 percent of teachers surveyed (and 70% of those with high-speed Internet connections) reported they had assigned Internet research tasks for their students during the school year. Use of the Internet to gather information for solving problems sometimes resembles a modern version of library research, in which students gather and synthesize information from published reports. Despite the fact that the task seems traditional, the characteristics of this new medium require special skills for students. The sheer volume of information allows students to study almost any topic, but also makes it more difficult to locate precisely the right information from among the thousands, or even millions, of sites that might be located. In addition, the ease of publishing and accessing materials on the Internet increases the likelihood that students will encounter inaccurate or biased information. As a result, students must learn new strategies for conducting searches and evaluating the information that they retrieve.
In addition to its function as a source of information, the Internet's capability for communication and interaction provides many innovative educational opportunities. Many times students are unable to find or understand the available resources. In such cases, teachers are also turning to ICT to link their students with mentors and subject-matter experts. In one such project, fourth-and fifth-grade students in McAllen, Texas , compared the experiences of their families on the Texas La Frontera to colonial life in the original thirteen U.S. colonies, with the help of the director of a historic preservation center and museum in Fredericksburg , Virginia .
Students carrying out scientific investigations can use the Internet to make observations and collect data. For example, fourth and fifth graders in California collected insects and sent them to San Diego State University . Using two-way audio and video connecting the school and the university, scientists guided the students in using an electron microscope to examine their specimens. Technology has made it possible to collect data from places students could never visit. In recent projects, high school students explored the floor of the Monterey bay by studying video from remotely operated robots, and middle school students were given time to use the Hubble telescope.
Students also use technology to collect data in their schools and communities. For example, using handheld computers outfitted with various types of probes, students can monitor the water quality at various locations in nearby streams or lakes. By transmitting their individual readings to a laptop computer in a field laboratory they can quickly graph their data and visually compare readings.
Using technology to summarize and present findings. In the past, students memorized and used formulas and models created by others to solve problems. Students often used these formulas, especially in the early stages of learning, with little understanding. In the early twenty-first century computer tools provide the opportunity for students to construct and test their own models using tools such as spreadsheets or concept maps. This type of instruction deepens students' understanding of abstract concepts and allows these concepts to be taught at an earlier age.
Once students have summarized their data and other information, they typically communicate their findings to others. In the past, this meant writing a report to be read by the teacher. Writing reports is still the most widespread use of ICT, with 61 percent of U.S. teachers assigning students word processing tasks. In addition to text, students also use computer-created graphics, video, and animations to communicate their ideas.
The teacher is not the only audience for students' presentations. Students are frequently expected to present their work and receive feedback from their peers and the world outside their classroom. Whether they are using presentation software to accompany a face-to-face presentation or developing materials to put on the Web, the trend is for students to be able to communicate and defend their work to a broad audience. This increases students' perception that problem-based learning is real work for real audiences.
Using technology for collaboration and distance education. There are many opportunities for individual students to use technology to enhance their learning. These include online courses that provide students in remote locations with opportunities for customized curriculum and advanced placement courses. These courses are conducted entirely online and offer asynchronous interaction among faculty and students. Because they allow students to participate anytime and from anywhere, online courses are becoming increasingly popular among postsecondary students whose job and personal commitments do not allow them to meet a regular class schedule.
Opportunities for interaction with peers from other countries can also contribute to knowledge and understanding of other cultures. ICT makes this type of communication possible for anyone with Internet access. For example, the KIDLINK project encourages students up to age fifteen to use the Internet to build a global network of friends. KIDLINK participants discuss issues ranging from how to make and keep friends to war and peace.
Teachers' Integration of Technology in Instruction
Although ICT is creating opportunities for fundamental changes in the way teachers teach and the way students learn, a recent survey indicated that only one-third of teachers feel prepared to use it effectively. This includes being able to use word processing, spreadsheet, presentation, and Internet browsing software. Such tools help teachers increase their productivity by preparing reports or lesson plans, taking notes, and communicating with colleagues and parents. These basic skills are necessary, but not sufficient, for creating changes in instruction. Changes require that teachers are familiar with ICT tools and materials in the subjects they teach. They must also be able to incorporate these resources into classroom activities that accomplish important learning goals.
Research has shown that learning to incorporate technology into instruction occurs over time and follows a pattern. Initially, teachers incorporate new technologies into the things that they traditionally do. Then, after observing changes in their students - including improvements in behavior, absenteeism, collaboration, and independent learning - teachers gradually begin to experiment and use technology to teach in new ways. It often takes four years or more from initial attempts until changes in student learning can be observed.
Research indicates that change at all levels will be necessary to bring about widespread and effective use of technology. Successful programs must devote a substantial portion of their budget to extensive professional development and technical support; they must encourage a culture of collaboration in which teachers work together to explore more effective uses of technology; and they must modify their assessment systems to measure changes, such as deeper understanding and improved problem solving, that result from effective technology use.
Future Trends
Advances in hardware and software have the potential to bring about fundamental changes in how technology is integrated and even in education itself. Computers formerly tethered to desktops by cables are being rapidly replaced by wireless laptop and palmtop models that free students to move about the school; collect, share, and graph data on field trips; and communicate their whereabouts and progress to teachers and parents.
Monitoring students' independent learning in these flexible environments will be supported by sophisticated new assessment technologies that will help teachers collect and analyze student data and make instructional decisions. These tools will continually assess students' work and provide feedback to them and their teachers. Such assessment has the potential to make time-consuming standardized testing unnecessary and to personalize the curriculum for every student. Ubiquitous, well-integrated technology tools will bring educators closer to redefining the educational enterprise and providing customized, just-in-time solutions for the learning needs of adults and children.
Internet Resources
Chen, Milton . 2002. "Bugscope: Magnifying the Connection Between Students, Science, and Scientists." http://glef.org/bugscope.html.
Electronic Emissary Project. 2001. http://emissary.ots.utexas.edu/emissary/.
KIDLINK. 2002. www.kidlink.org.
National Center for Education Statistics. 2000. "Internet Access in U.S. Public Elementary and Secondary Schools." http://nces.ed.gov/pubsearch/pubsinfo.asp?pubid=2000102.
Passport to Knowledge. 2001. http://passporttoknowledge.com/hst/.
United Nations Development Program. 2001. "Human Development Report 2001: Making New Technologies Work for Human Development." www.undp.org/hdr2001/.
University of Washington , Tacoma 2001. "Conductivity and Temperature Study." www.Tacoma.Washington.edu/education/intel/Projects/Morrison_photo.htm.
Applications of IT :
A fourth trend is the ever-increasing array of applications that make IT more useful. Computers were originally used primarily for data processing. As they became more powerful and convenient, applications expanded. Word processing, spreadsheets, and database programs were among the early minicomputer and PC applications. Over the past two decades, innovations in software have enabled applications to expand to include educational software, desktop publishing, computer-aided design and manufacturing, games, modeling and simulation, networking and communications software, electronic mail, the World Wide Web, digital imaging and photography, audio and video applications, electronic commerce applications, groupware, file sharing, search engines, and many others. The growth and diversity of applications greatly increase the utility of IT, leading to its further expansion.
In the 1960s, computers were used primarily in the R&D community and in the offices of large companies and agencies. Over the past few decades, the expansion of applications has contributed to the rapid diffusion of IT to affect nearly everyone, not just the relatively few people in computer-intensive jobs. IT has become common in schools, libraries, homes, offices, and businesses. For example, corner grocery stores use IT for a variety of electronic transactions such as debit and credit payments, and automobile repair shops use IT to diagnose problems and search for parts from dealers. New IT applications are still developing rapidly; for example, instant messaging and peer-to-peer communication systems such as Napster are examples that have become popular in the past 2 years. See sidebar, "Peer-to-Peer Applications."
Networking :
The third trend is the growth of networks. Computers are increasingly connected in networks, including local area networks and wide area networks. Many early commercial computer networks, such as those used by automated teller machines and airline reservation systems, used proprietary systems that required specialized software or hardware (or both). Increasingly, organizations are using open-standard, Internet-based systems for networks.[2] As people have been able to interconnect and share information with each other, the value of IT has increased. See sidebar "Metcalfe's Law."
The growth in networking has been enabled by rapid advances in optical networking. In 1990, a single optical fiber could transmit about 1 billion bits per second; by 2000, a single fiber could transmit nearly 1 trillion bits per second (Optoelectronics Industry Development Association 2001).
The growth in networking is best illustrated by the rapid growth of the Internet. Worldwide, there were nearly 100 million Internet hosts—computers connected to the Internet—in July 2000, up from about 30 million at the beginning of 1998. (See figure 8-4 .) Networking is evolving in several ways: more people and devices are becoming connected to the network, the speed and capacity of connections are increasing, and more people are obtaining wireless connections. See sidebar, "Wireless Networking."