Mission accomplished: “The Human Genome Project” was in the bag by 2003.  Now we understand how humans are genetically wired, right?  Not so fast.  Another human genome was just published, raising a whole new set of questions.  The big issue is that we all have two genomes in one – one from each parent.  Biologists knew this, of course, but for the first time, those two genomes were untangled from one another, and a lot of differences were found: two million, in fact.  How do our two separate genomes behave toward each other?  And if genomes differ this much, what does a concept like “the human genome” really mean?

The Max Planck Institute for Molecular Genetics just published the dual genomes of a 51-year-old German male.  (This contrasts with the mixed genomes from several individuals used in the Human Genome Project.)  A write-up on Science Daily explained,

Current sequencing technologies do not deliver both sets of chromosomes separately but instead provide a composite of both versions. Therefore, the scientists had to develop a new method to be able to identify the different sequences of genetic letters for both versions of the chromosomes separately. “In essence, we each have two genomes, inherited from each of our parents, and we need to look at these separately and at their interactions to fully understand the biology of genomes,” says Margret Hoehe, leader of the research group. “We constantly refer to ‘the’ genome. However, it is essential for the development of personalised medicine that an individual’s two sets of chromosomes are considered separately as they can differ regarding their genetic codes and, consequently also, their encoded functions.”

The team found many differences between them.  “Importantly,” the article stressed, “90 percent of the genes exist in two different molecular forms.”  They differed at two million positions, and three million base pairs (single nucleotide polymorphisms, or SNPs).  Further, “Between 60 and 70 percent, i.e. the majority of the genes, only arise in their characteristic molecular forms in the individual whose genome has just been analysed.”  Hoehne explained that this means “that the biology of genes and genomes has a strong individual component.” ….

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