From DNA to Genomics
Almost every cell in your body is loaded with molecules called DNA. Each DNA molecule is made of chemicals called “bases” nicknamed A, T, C, and G (for adenine, thymine, cytosine, and guanine). The bases occur in pairs, organized into a twisting, ladder-like structure, the famous “DNA double helix.” The ordering of the base pairs in the helix creates a set of instructions that are the blueprints for you to grow and live. The whole set of instructions is your genome.
Sections of your genome (genes) tell your cells what proteins to make. Each protein plays a distinct role, such as the protein keratin that makes fingernails strong or the protein crystallin that makes the lens of your eye transparent. Protein manufacture is the foundation for a living being. Your genome is unique to you and determines what traits you have. Many traits are determined by more than one gene, in some cases by tens or hundreds of genes.
Genomics is the science of mapping and sequencing genomes and analyzing their structure and function. The entire human genome was sequenced by teams of researchers from 1990-2003. The Human Genome Project identified the more than 20,000 genes in the human genome and created a huge digital database of information.
Additionally, thanks to modern techniques that reveal the sequences of base pairs in any organism, a new field of “comparative genomics” has emerged. Comparative genomics is the study of the evolutionary relationships of organisms and their traits using genetic information. Some parts of the genome change as species diverge and new species are formed. Other parts of the genome remain the same and code for similarities among related organisms. By comparing the genomes of organisms, scientists can figure out how natural selection has acted over time and draw evolutionary trees of species relationships. They can even use DNA-based trees to propose how species may have moved across the globe during earth’s history.
For example, Smithsonian botanist Dr. Jun Wen compares the genomes of the grape family to better understand their evolutionary relationships. A team of Smithsonian researchers, including Dr. Warren Wagner and Dr. Helen James, have used genetic information to uncover the geographic story of colonization and diversification of plants and animals across the Hawaiian Islands. Smithsonian botanist Dr. Elizabeth Zimmer has been able to identify sections of the DNA in green plants that, because they have an important role in making proteins, are conserved over hundreds of millions of years.
Comparative genomics also has promise for better understanding the evolution of the human genome in ways that may help us fight disease. For example, comparative genomic research has shown that about two thirds of the genes that are associated with cancer in humans also occur in fruit flies. When a gene causing Parkinson’s disease in humans was added to the fruit fly genome, fruit flies acted like they had Parkinson’s. Unexpectedly, fruit flies, in addition to lab mice, then could become future test organisms for Parkinson’s treatments for humans.
DNA barcoding is a new application of genomics techniques. The genomes of most species are more similar than different. For example, what distinguishes a human from a chimpanzee is only about 2% of its genome. The barcode is a short sequence of DNA of a well-known gene, selected for its ability to distinguish species. You can barcode an organism for a few dollars in little more than a day in the laboratory. This makes DNA barcoding accessible for large scale research projects. A consortium of researchers from across the globe have launched the International Barcode of Life that seeks to create a digital library for all life, based on DNA barcodes.
At the Smithsonian Natural History Museum, botanists Drs. David Erickson and John Kress have barcoded every plant species on a tiny island in the Potomac River, part of a global effort that may lead to use of a handheld device to reliably identify any plant you come across by its DNA. On a larger geographic scale, the Moorea Biocode Project, directed by Smithsonian zoologist Dr. Chris Meyer, aims to barcode every species of multicellular organism on the Pacific island of Moorea. Smithsonian researcher Dr. Carol Baldwin led a project to barcode DNA for hundreds of species of Caribbean fish. She found that the barcodes can be used to determine the adult species corresponding to larval fish that otherwise are difficult to identify.
Besides biological research and conservation, there are many practical uses of DNA barcoding. For example, the work of Smithsonian botanist Dr. John Kress and others to barcode plants may allow the Food and Drug Administration (FDA) to detect undesirable plant material in herbal teas. The FDA also uses the DNA barcoding protocol developed by Smithsonian’s Dr. Lee Weigt to detect incorrect labeling of fish on the food market, such as cheaper fish passed off as red snapper.
Smithsonian ornithologist Dr. Carla Dove heads an unusual sort of forensics team that analyzes the remains of birds that are struck by airplanes with sometimes disastrous results. Research assistant Nor Faridah Dahlan extracts DNA from the bird remains and compares it to a national library of DNA barcodes for birds to see what species were struck.
Into the Future
DNA sequencing has tremendous implications for conservation of biodiversity. It provides a new way of cataloguing the species on Earth and looking at their evolutionary relationships. Genomic information is being added to the Encyclopedia of Life, an online, freely accessible database set up to maintain information about every species known on Earth.
The work of the Human Genome Project has advanced efforts to understand the genetic bases of illnesses. Scientists studying cancer or other specific illnesses now can use genomics on individual humans and even on individual types of cancer cells to understand relevant disease genes at a cost similar to CAT scans and MRIs.
As techniques to study DNA continue to evolve and become readily available, genomics will become an even bigger part of our shared future.