Human Genome Individuality Adds New Questions
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.”
This has profound consequences for human health. When mutations are found on one gene, they can be compensated for by the normal gene—if that gene is dominant. For instance, in this individual, there were two mutations on one chromosome in the infamous BRCA1 gene known to be involved in breast cancer, but since the other was normal, the individual had a healthy copy. “Overall, the scientists identified 159 mutated genes in their test subject with a disease-predisposing potential, which can impair the function of proteins,” the article said. “In 86 of these genes, the mutations were found in the same copy of the gene.” Having two copies of the genes can thus act as a mutational sponge to avoid disease. “A gene can only make a person sick if one form of it overrides the other or if both copies are affected.”
The researchers noted that their findings raise “new and fundamental questions” about genetics, including, “How do the two different molecular forms of a gene behave towards each other? Do they work together or against each other? Which of the two gene forms is dominant and why?” It’s clear that the mixed genomes sequenced to date, not only in humans but in many other organisms, may be obscuring the answers to these fundamental questions, including the phylogenetic inferences drawn from genomes that may turn out to be non-representative. These worries, combined with the rising interest in epigenetics (non-coded heritable structures and functions), and the “strong individual component” in our personalized genomes, raise an even more vexing question: how much do we really know what we think we know about molecular biology?
Well, one thing we know as FACT is that evolution is a fact fact FACT and anyone who dares question it is an anti-science, bigoted nincompoop. (This said to pacify our gracious and thoughtful skeptical friends, and to spare them depression caused by the shattering thought of scientism being vulnerable.)