Sociogenomics 2: Why You Can’t Clone a Calico Cat There's a country music song in there somewhere. Calico cats are white with red and black patches. Apparently some couple with more money than sense paid to have their dear departed calico cloned. But several attempts failed to produce a cat that looked like Furball, or whatever they called the deceased. Instead they bought, for thousands, cats that were all one color or another. Someone might have bothered to tell them that what they were trying to do was destined to fail.
Calicos are all females, and their hair color is determined by a gene on the X chromosome. But here is the cool thing: the chromosome contains two complete sets of genes, one from each parent. In order for that to add up to a functioning cat, one set has to be turned off in each cell. This happens in patches, hence the tortoise shell color pattern. Now when they went to clone Furball, they took just one cell and used the nucleus to launch FB2. But in that one cell, only one set of genes was turned on, and that was fixed for the whole new cat.
I haven't had so much fun since grandma caught her x chromosome in the ringer. Here is the scoop: we understand how genes work. They are molecules, and we know how they code for RNA and how proteins are built form that. We have a pretty good idea about the factors that determine which genes are expressed, and it is clear that the environment can affect that process. I know a whole lot more about exons (sections of DNA that code for proteins), introns (sections of DNA that have to be edited out, but may play a role in expression), promoters (sections that call for a polymerase gene reader, than I did yesterday.
We also know that genes are responsible for all sorts of wonderful and terrible things that happen in development. But while mapping the genome has made it a lot easier to find a gene, it hasn't made it easier to determine how the gene actually produces an effect on the phenotype (the actual organism).
It is pretty certain that there is such a thing as general intelligence, or G. Sorry for all of you who think there are all sorts of Gs out there, and that everyone has at least one of them. A condition known as Fragile X syndrome produces a child (almost always a boy) with low IQ and low tolerance for stress. The gene has a long repeat of a three letter DNA sequence, and this shuts the gene down a lot before it can bond with RNA. The result is a bunch of fuzzy dendrites (part of the neurons that make the brain work). That doesn't mean we have "the gene" for general intelligence; it does mean we have a gene necessary for a well functioning brain and can tie it tight to a specific disorder.
Another genetic disorder was discovered that resulted in a pronounced tendency toward violence in one Dutch family.
Hans Brunner, a geneticist at the University Hospital in Nijmegen, has found that the violent male members of the Dutch family mentioned earlier in this paper, lacked a gene that produces monoamine oxidase-a (MAOA) (4). MAOA is an enzyme that breaks down significant transmitters in the brain. If the MAOA does not break down these transmitters - specifically, serotonin - then buildup of serotonin will occur and could cause a person to act violently (3).
So far, no studies have found such a link outside that one family. In this case, like the former, what made a determination of genetic causation possible was that a single gene was the culprit. But it seems very certain that more complicated arrays of genes and gene expression factors will turn out to play a significant role in a lot of good and bad behaviors. This doesn't mean genetic determinism. How genes are expressed is greatly affected by the environment, and the environment can be controlled, to some extent, by deliberate action. But to deliberate properly, we need to know more about the mechanics of DNA.
All human thoughts and actions happen because the brain works the way it does. It works that way in large part because of the extraordinarily complex structure of the human genome. We are getting a few peaks into that subterranean architecture right now.