by Carol A. Westbrook
Less than 100,000 people in the entire world have had their genome sequenced. I am now one of them. As I wrote in 3QuarksDaily in December, I went into this with some trepidation–you never know what bad news lurks in your genome! I promised to give a report of my results, and here it is.
To get my genome sequenced, I enrolled in Illumina's “Understand Your Genome” Program. Illumina is one of the few companies licensed by the FDA to perform whole genome sequencing (WGS) for medical diagnosis–other consumer products such as Ancestry.com, National Geographic's Geno 2.0, and 23andMe, provide only a limited analysis. I sent in a blood sample in November, and in February received a detailed analysis by Illumina's genetic counselors. In March I attended the “Understand Your Genome,” conference, where I received an iPad with my WGS uploaded into the “MyGenome” app, training on the use of the app, and a fascinating daylong seminar which explored the interpretation and medical uses of genome sequences. My daughter, a medical student, attended the program with me.
Viewed on the iPad, my genome sequence consists of two similar but not identical, parallel lines of the letters, one from each chromosome. There are only 4 letters, A,C,G, and T, representing the four DNA nucleotides that are aligned to make the sequence. A human sequence is about 6 billion nucleotides long, with half inherited from one parent and half from the other, and a few new mutations that arose on their own, probably less than 100. Thus, from a family perspective, a person's DNA sequence is 50% identical to each of his parents, children or siblings, 25% identical to grandparents, grandchildren, and so on to my distant relatives. My genome is very similar to every other person's, but it is not identical to anyone's. No one has ever had the same DNA as me, and never will — it is what makes me uniquely me.
How different am I from everyone else? My genetic analysis showed that I have 3,524,186 individual nucleotide differences, from the “average” genome to which it was compared, reference genome hg19, NCBI build 37. This is about 0.05% variation, which is typical for most people. To put this in perspective, if you were to compare my DNA to that of our two most closely-related primate species, bonobos and chimpanzees, the differences would be over 4%; when comparing me to Neanderthal man, however, you would find only 0.3% variation. So 0.05% is small enough to make me human, but large enough to make me a unique individual.