What Makes All the Difference

In the passing year more than ever before, researchers have come to realize how genetically different we are from each other. Technological advancements have led to significant improvements in genome-sequencing abilities, and as a result – to better understanding of the human genetic diversity and of genetic variations associated with various diseases.
 The cover of 21 December 2007 cover of Science magazine announcing Human Genetic Variation to be 'Breakthrough Of The Year', on the background of a T-shirt bearing an annotated gene-sequence map of human chromosome 1 (Credit: Science magazine/Joe Zeff Design)
The cover of 21 December 2007
Science Magazine announcing Human
Genetic Variation to be ‘Breakthrough
Of The Year’, on the background
of a T-shirt bearing an annotated
gene-sequence map of human chromosome 1
(Credit: Science Magazine/Joe Zeff Design)

More than 99 percent of any person’s DNA is identical to any other person’s DNA. Genetic variation in humans refers to differences in DNA sequences among individuals and is the key to some of the differences, such as eye color, blood type, and the risk for particular diseases.

Two versions of the human genome were published in 2001, both of which greatly underestimated human genetic diversity. Due to improvements in sequencing technologies, major advances have recently been accomplished in this field. These advances made researchers realize, in 2007, that the extent to which our genomes differ from person to person is much wider than previously estimated. As genomic variation has comprehensive implications for deciphering the genetics of complex diseases and personal traits, the progress made in its understanding will probably affect various aspects of our lives – from how doctors treat diseases to how we protect our privacy. “Human Genetic Variation” was therefore recognized as “The Breakthrough of 2007” by Science magazine.

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More than a dozen genome-wide association studies were published in 2007. In these studies the genomes of thousands of individuals with and without certain diseases were rapidly scanned for genetic markers in order to find genetic variations associated with the diseases. The new genetic associations identified may enable researchers to develop better strategies to detect, treat, and prevent these diseases. Diseases into which genome-wide association studies have already provided insight include atrial fibrillation, autoimmune diseases, bipolar disorder, breast cancer, colorectal cancer, type 1 and 2 diabetes, heart disease, hypertension, glaucoma, Crohn’s disease amyotrophic lateral sclerosis, multiple sclerosis and rheumatoid arthritis.

The human genome consists of six billion pairs of bases called nucleotides. Since it has been sequenced, biologists have been charting single-nucleotide polymorphisms (SNPs) – minute variations of one base. Genomes can differ in many other ways, as thousands to millions of nucleotides can get lost, added, copied or turned around in ways that can change genetic activity within a few generations. In 2007 researchers became aware that these changes affect more bases than SNPs. The first sequenced human genome of a single individual (rather than a mosaic of DNA sequences from various donors), published in 2007, enabled scientists to compare both chromosome sets (one set inherited from each of his parents) and significantly promoted this awareness. This sequencing, published by the J. Craig Venter Institute, was separately covered by TFOT.

It is important to note, however, that investigating the human genetic variation and promoting the great promise for improving health through personalized medicine and understanding may also constitute a great threat, and that we must carefully consider the risks for discrimination and loss of privacy.