A form of a gene. Most human genes come in different forms. For example, one form of the APOE gene may protect people against Alzheimer’s disease while another may be a risk factor.

A “cutting-and-pasting” process by which cells splice together elements of the same gene to make different proteins. That’s how the human body manufactures more than 100,000 proteins from a set of about 30,000 genes.

The twenty molecules that are the building blocks of proteins.

A family of microorganisms that evolved separately from bacteria, plants, and animals. Some live in extreme environments, such as thermal vents deep in the ocean.

See Extremophiles

A molecule, derived from bacteria, used to carry the DNA of humans or another species in genetics research.

Microorganisms that consist of a single cell. Bacteria, like all living things, have their own genomes. They also have the ability to exchange genes with other bacteria. This “swapping” of DNA may help explain how genes that confer resistance to anti-bacterial drugs have spread among many species.

Unit of DNA commonly used to measure the size of genomes. The human genome has three billion base pairs, or DNA “letters” (A, T, C, and G).

See Nucleotide

The science of using computers and sophisticated mathematics to sort and analyze large amounts of biological data.

The science of using living things, such as plants and microorganisms, to remove toxins from the environment and restore it to a healthful condition.

News about Toxic Cleanup

A microscopic form of life. Cells are complex entities in and of themselves, capable of carrying out the biochemical processes necessary to stay alive and, when the time comes, to die.

Where genes are found. Chromosomes are the structures in cells that “package” genes and ensure their safe transfer into new cells. A person has 46 chromosomes, half of which were inherited from each parent. Dogs have 78 chromosomes; cats have 38.

News about Chromosomes

The science of comparing the genome sequences of humans and other species in order to discover similarities and differences in biology. For instance, scientists who study evolution might compare the genomes of humans and chimpanzees, while scientists who study the bacterium E. coli might compare strains that harm humans and those that do not.

News about Comparative Genomics

A disease that involves multiple genetic and environmental factors. Obesity, heart disease, and schizophrenia are examples of diseases that have multiple causes.

The study of communities of organisms in nature using the tools of genomics. Sequencing the DNA of microorganisms found in a liter of ocean water is an example of community genomics.

News about the Environment

A molecule found in all living things that carries genetic information. DNA looks like a twisted ladder, and consists, primarily, of four chemicals known by their abbreviations: A, T, C and G.

See Nucleotide

A technique for identifying a person or an organism. A “DNA fingerprint” is a composite of short, repetitive segments of DNA that vary from person to person.

A device for monitoring the activity of genes. Most DNA microarrays are glass slides or microchips “embedded” with thousands of genes. DNA microarrays have many applications in research and have been used, for instance, to identify genes involved in cancer and to develop drugs.

See Gene Expression

The sequence of genetic “letters,” or nucleotides, in a piece of DNA. For instance: ACGTACGTACGT

The study of “environmental,” or non-genetic, factors inside cells that influence the ways genes produce proteins.

The study of communities of organisms in nature using the tools of genomics. Sequencing the DNA of microorganisms found in a liter of ocean water is an example of environmental genomics.

News about the Environment

The parts of a gene used to make proteins.

An organism that lives in an extreme environment such as ice in Antarctica, Chilean deserts, and thermal vents deep in the ocean. Most extremophiles are microorganisms, but a few species of plants and animals, including certain worms and snails, endure extremely harsh conditions.

News about Extremophiles

A piece of DNA used by cells to manufacture proteins, which carry out the business of cells. Each human gene is a template for one or more proteins.

The “turning on” of a gene. Most human genes are active, or turn on, only in certain cells under certain conditions. Genes for eye color are active in eye cells but not in stomach cells. Similarly, some genes may lie dormant for years and then turn on and become malignant late in life.

A technique for classifying cells, such as tumor cells, based on the activity of their genes. Research physicians use the technique in diagnosing disease and in selecting therapies for patients. Eventually this technique may be useful in the general practice of medicine.

See DNA Microarray

News about Gene Tests

An experimental field of medicine that aims to treat disease by delivering to patients new copies of a gene that is missing or not working properly in their bodies. To date there have been no unqualified successes in gene therapy, and the field has struggled to find safe and effective methods of delivering therapeutic genes to where they are needed in the body.

The study of genes and how they are inherited. Traditionally, genetic studies have focused on one gene at a time, while genomics is the study of large numbers of genes.

A collection of genes. The human genome is the collection of human genes, just as the dog genome is the collection of dog genes. All living things have genomes. Plants, animals and bacteria included.

A genome contains the biological information for building, running, and maintaining an organism—and for passing life on to the next generation. Nearly every cell in your body contains a complete copy of your genome; so, in fact, you actually have a trillion genomes because scientists believe the human body contains about a trillion cells.

The German botanist Hans Winkler coined the term genome in 1920 by combining the words GENe and chromosOME. A precise definition of genome is “all the DNA in a cell” because this includes not only genes but also DNA that is not part of a gene, or non-coding DNA.

See Non-Coding DNA

News about Genomes

The sequence of consecutive DNA “letters” spanning all the chromosomes of a cell from start to finish.

A Quick Guide to Sequenced Genomes

The study of large numbers of genes, or genomes. Genetics, by contrast, tends to focus on one gene at a time.

The particular form of a gene a person has.

To determine, though a DNA test, the particular form of a gene a person has. For instance, Alzheimer’s researchers may genotype a patient’s DNA to learn which form or forms of the APOE gene the person has.

A collection of variable DNA sequences that tend to be inherited together.

An international effort to identify variable DNA sequences across the human genome in different ethnic populations. The project is mapping collections of DNA variations, or haplotypes. When complete, the “Hap Map” will be used to study genetic variations associated with disease and the different responses people have to drugs.

A gene that behaves one way when inherited from the father and another way when inherited from the mother. For example, the paternal copies of some imprinted genes are never “turned on,” or activated.

News about Genomic Imprinting

Parts of a gene that are not used to manufacture proteins.

DNA in the genome that is not directly involved in making proteins or other molecules.

About 98 percent of the human genome consists of non-coding DNA. The term “junk” reflects the outdated belief that this DNA accumulated over the course of evolution and no longer serves a purpose in humans. But it’s now clear that some non-coding DNA controls the activity of genes and may have other functions.

A disease caused by a single gene that is inherited in a straightforward manner from parent or parents to child. Huntington’s disease and cystic fibrosis are examples.

The term "Mendelian" refers to Gregor Mendel, an Austrian who did pioneering work on genes and traits in ordinary garden peas by showing that a single trait, such as color, can be determined by a single gene. Compared to “complex diseases,” Mendelian disorders are relatively rare.

See Complex Disorder

Small molecules found in plants and animals that may regulate the activity of genes.

The smallest number of genes an organism needs to stay alive in a particular environment. A goal of research on the minimal genome is to design synthetic microorganisms that can perform useful tasks such as generating biological forms of energy.

A creature, like the mouse or the fruit fly, used in the laboratory to study biology. Many genes in humans are found in other species, and biologists study model organisms to learn about how these genes might operate in the human body.

DNA in the genome that is not directly involved in making proteins or other molecules.

About 98 percent of the human genome consists of non-coding DNA. The term “junk” reflects the belief that the DNA, which is often repetitive, no longer serves a purpose in humans. But it’s now clear that some non-coding DNA controls the activity of genes and may have other functions.

A single genetic “letter”; a nucleotide is one of the four chemical subunits of the DNA molecule, also called a base. They are known by their abbreviations A, T, C, and G.

See Base Pair

The information center of a cell. The genetic information of most living things is physically located in the nucleus of a cell, which contains chromosomes, where genes are found.

The science of how a person’s genes affect his or her response to drugs.

Research in pharmacogenetics has two goals. One is to identify people whose genetic make-up would make them sick or even die from taking a particular drug. If researchers can identify variations in genes that influence a person’s response to a drug, then DNA testing could reveal which patients should avoid the drug. The second goal is to predict who is most likely to benefit from one drug rather than another. The word is used interchangeably with pharmacogenomics.

The science of how a person’s genome affects his or her response to drugs, in either a positive or negative way. The word is used interchangeably with pharmacogenetics.

A physical trait such as red hair, or behavior such as anxiety. A phenotype results from the “expression” of a gene or genes.

A molecule that carries out the business of cells. Enzymes and hormones are types of proteins. Most proteins have folds and bends, and their three-dimensional structures allow them to interact with other proteins, forming dynamic networks.

News about Proteomics

A collection of proteins. The human proteome is the collection of proteins found in the human body. A proteome can also refer to the set of proteins in a particular cell.

The study of proteins on a large scale.

News about Proteomics

DNA that controls the activity of genes. In the human genome, regulatory DNA sequences tend to be short and located near the genes they control.

A molecule involved in manufacturing proteins that may also regulate the activity of genes.

A system in cells for “turning off,” or silencing, genes. Some plants use RNAi to silence the genes of invading pathogens, and some animals may as well.

In the laboratory, scientists mimic RNAi to test the functions of individual genes. The system has potential as a therapy if scientists can figure out how to trigger the silencing of “overactive” genes in people, such as those involved in cancer.

News about RNAi

The sequence of genetic “letters” in a piece of DNA. A short DNA sequence might be: ACGTACGTACGT

A Quick Guide to Sequenced Genomes

To determine the sequence of genetic “letters” in a piece of DNA or an entire human genome.

A method of determining the DNA sequence of a genome.

The first step in shotgun sequencing is to copy a genome many times, then shred the copies into fragments of DNA that can be “read” by machines. Next, computers identify the fragments that belong next to each other in the genome and assemble them into a complete genome sequence.

A disease caused by a single gene that is inherited in a straightforward manner from parent or parents to child. Huntington’s disease and cystic fibrosis are examples.

The term "Mendelian" refers to Gregor Mendel, the Austrian who did pioneering work on genes and traits in ordinary garden peas by showing that a single trait, such as color, can be determined by a single gene. Compared to “complex diseases,” Mendelian disorders are relatively rare.

See Complex Disorder

A single “letter” of DNA that may vary from one person to the next. At a particular location in the genome, one person may have an “A” while another has a “T.” In the human genome, a SNP occurs on average about once every thousand DNA “letters.”

An “immature” cell that can become any type of cell in the body. Scientists are investigating ways to coax human stem cells into becoming replacement cells for people with diseases.

News about Stem Cells | Stem Cells: Policies and Players

The science of how a person’s genome affects his or her response to potentially toxic substances in the environment, such as pollutants. A goal of research in toxicogenomics is to identify the genes that predispose some people to become sick when they encounter toxins in their daily lives.

A physical characteristic, such as red hair, that has a genetic component.

The process of “turning on,” or activating, a gene.

A quasi-living thing that infects another cell and uses the host cell to make new viruses. Viruses cannot live or reproduce outside another cell.