4. Background to the science of genetics and modern applications of it
For the best general introductory article you can read online about the science of DNA testing, read The Y Chromosome In The Study Of Human Evolution, Migration And Prehistory by Neil Bradman and Mark Thomas of The Centre for Genetic Anthropology at University College, London (UCL).
Do also take the time to view the Dolan DNA Learning Center's excellent animated primer on DNA, genes and heredity.
The Atlantic Monthly's April 2001 edition ran a long article titled 'The Genetic Archaeology of Race' that focused on the Human Genome Diversity Project and the work of Luigi Luca Cavalli-Sforza. The article highlights the paradox at the heart of human genetics: the only way to understand how similar we are is to learn how we differ, yet any study of human differences seems to play into the hands of those who would accentuate them. It points out that the term 'race' is meaningless in a genetic sense. "The genetic variants affecting skin color and facial features are essentially meaningless; they probably involve a few hundred of the billions of nucleotides in a person's DNA. Yet societies have built elaborate systems of privilege and control on these insignificant genetic differences."
For a general introduction to DNA testing from the family history perspective read Candace L. Doriott's article in the January/February 2000 edition of the online magazine at www.ancestry.com: Genetic Codes Unraveled: New Clues to Human History and the follow-up September/October 2000 article Solving the Mystery: DNA Tests for Your Research. Factsheets describing the contents of BBC Radio 4's five-part summer 2001 series Surnames, Genes and Genealogydescribe Dr Sykes's work in easy-to-understand terms.
For a detailed description of DNA testing aimed at non-scientists go to the online journal Scientific Testimony. Another good site to explore is Dr Ralph Rascati's course notes at Kennesaw State University, Georgia. The Encyclopedia of Life is a subscription site that offers one time 24 hours' free access to explanatory DNA resources while Eric Weisstein's Treasure Troves of Science is open to all.
For a detailed description of mitochondrial DNA analysis look at the Mitotyping Technologies website. For the types of STR (short tandem repeat) testing and DNA profiling look at the 101 guide at NIST's online database of STRs. Detailed primers on Molecular Genetics and a glossary of terms used in the study of genetics are also online.
The Human Genome Project
The human genome is the complete list of coded instructions needed to make a human being. The four letters of the DNA alphabet (A, C, G and T) carry the instructions for making all organisms; each set of three letters corresponds to one of twenty different amino acids. There are three billion letters in the DNA code in every one of the 100 trillion cells in the human body. Each cell contains some 6' (2 metres) of DNA packed into a structure only 0.0004 inches across. If all of the DNA in the human body was put end to end, it would reach to the sun and back more than 600 times. The information contained in it would fill a stack of paperback books more than 60 metres high, the equivalent of 200 500-page telephone directories. DNA differs by only 0.2 percent, or 1 in 500 bases, among humans, and human DNA is 98% identical to that of chimpanzees.
Individual humans have perhaps 2.1 million genetic letters that are different from each other though only a few thousand of those differences account for the biological differences between them. All humans are thus essentially identical twins. The genome project's genetic data confirms that there is no scientific basis for the concept of race as people from different racial groups can be more genetically similar than individuals within the same group. Genetic studies show that there is more variability in the gene pool in Africa, than outside. As one expert puts it, "from a genetic perspective, all humans are Africans, either residing in Africa or in recent exile."
The best public site is the US government's Human Genome Project portal. For details on the human genome project itself and the sequencing of the c.31,780 human genes go to Celera, the private firm co-authoring the sequence, and the Sanger Centre, leading the academic project. (Note that the actual number of genes in the genome is still disputed!) There are good explanations in BBC reports on the results, the gene code at a glance, a flash presentation on how the sequencing process was done and from The Guardian a description of the next areas of investigation, protein studies and the proteome.
Science Magazines & Searches
Science Functional Genomics and Nature Genetics are two scientific magazines with archive materials. Abstracts of key articles on genetics can also be found by searching the website of the American Association for the Advancement of Science on a free subscription.
There are several projects to gene map entire communities in different places around the world:
The largest and most controversial is in Iceland where DeCode Genetics, a start-up genomics company, has a project to map the genome of the Icelandic people in help locate multi-factorial diseases. Iceland has a series of distinctive characteristics that suit it for genetic analysis in adition to its admirable qualities as having the world's longest standing parliament and a 100% literacy rate. Its population is relatively small: today it is 275,000 but in the recent past it was as low as 50,000. There are an unusually complete set of family records in Iceland: over 80% of all Icelandic people who ever lived can be placed genealogically and the population is understood to be highly homogeneous. There are also comprehensive clinical records of Iceland's public health service dating back to 1915. Background to the project can be found at a site at UC Berkeley in conjunction with the Institute of Anthropology at the University of Iceland, a BBC report from February 2000, and from DeCode Genetics's own website.
The 108,000 inhabitants of the South Pacific island of Tonga will be studied by the Melbourne-based biotechnology company Autogen to assist its diabetes and obesity research. Both conditions are prevalent on the South Pacific island. Populations on remote islands are in general ideal for genetic research because communities are fairly static and families often trace back their family trees over several generations.
The small Italian village of Cilento some two hours' drive from Naples, one of nine villages that are genetically relatively self-contained communities that the Italian government now wants to turn into 'Genetic Parks' to stimulate biotech research.
DNA analysis is a key tool in the fight against hereditary diseases and the use of DNA testing is being promoted to families in the United States with this in mind. For reference, the U.S. Department of Health & Human Services has an interesting portal built around gene testing. The Morrison Institute for Population and Resource Studies at Stanford University has a good FAQ on its Human Genome Diversity Project plus other links. The latest research results suggest that there are discrete blocks of DNA that differ from one person to the next which may be common enough and account for enough of the genome that scientists will need to draw a new map of the genome that takes account of its blocky structure. This haplotype map would be a key tool to help pin down the genes that contribute to the development of complex diseases such as cancer, diabetes, and mental illness.
A good starting place to understand current research for specific conditions is the NORD website. NORD is a federation of more than 140 not-for-profit voluntary health organizations serving people with rare disorders and disabilities. It defines a rare or 'orphan' disease as one affecting fewer than 200,000 people in the United States. There are more than 6,000 such rare disorders that cumulatively affect approximately 25 million Americans or one in every 10 people. For information about these rare diseases look at the Office of Rare Diseases which carries materials including current & completed research and publications from scientific and medical journals. Other interesting sites are the Hereditary Disease Foundation, which focuses on Hungtington's disease and whose research in 1983 identified a genetic marker for it demonstrating for the first time that the newly-developed DNA markers could be used successfully to map human genes, and the Howard Hughes Medical Institute. Some diseases are family specific.
The BBC recently reported the case of the West Cumbrian Coulthard family whose members regularly suffer from what has been termed neuorferritinopathy, a condition that mimics Parkinson's & Huntingdon's diseases. Most recently it has been reported that most eyesight problems are genetic and that one's genetic make-up plays a large part in pre-determining one chances of developing Alzheimer's. The latest thinking is that many of our attitudes could be defined as genetically determined.
These areas are outside of the scope of this portal but is included here for reference. The type of tests offered by family history labs can't be used to determine paternity queries. There are many companies that offer these types of services, typically used to provide evidence required in legal cases. One in the USA is DNA Testing.com and another in Germany is Papacheck. Forensic DNA testing links generally to criminal cases, including long-unsolved cases like this one from the UK. You can also view the British Forensic Science Service's site.