You are a collection of cells (literally trillions of them), each with a specific design and function. However, with a few exceptions, your cells all have a basic architectural design. Most of the time they are depicted as looking like a fried egg cooked sunny side up, but in reality they are three dimensional beings, more akin to a golf ball that you’ve cut across its midline. The “white” of our cell model is the body of the cell, and here are found many specialized areas called organelles that do particular jobs, much like our own internal organs have specific jobs as well. The “yolk” of our cell model is called the nucleus, and in this compartment there lies the object of our affections, the chromosomes.

Chromosomes were first discovered at the end of the 19th century by a German biologist named Walther Flemming. Flemming was looking at cells under a microscope and got the idea to use colors to dye the cell to make it easier to see things. The idea must have worked better than anticipated since he at once began to see spaghetti looking things in the nucleus that dyed a very deep color. As is the fashion, he named these entities chromosomes which is Greek for “colored bodies”.

Chromosomes are one of the more dynamic faces of Nature; they have to be, since they are responsible for the passing on of the 'Baton of Life' that we call reproduction. The number of chromosome in the cell nucleus differs somewhat from species to species. We humans have 46 chromosomes; dogs have 78; alligators 32; cabbage plants 18.

Your chromosomes are both the governess and chauffeur of the most important molecule in your body: DNA --which is actually two molecules wrapped around each other. Like any blueprint, DNA needs to be read in order for the work order to be constructed. Now, DNA is a long, long molecule. If it were completely unraveled it would be about six feet long, yet so thin that it would be invisible, since you can easily fit one million cells on the head of a pin. If the entire DNA, in every cell of your body, was stretched out and laid end-to-end in a straight line, it would reach to the sun and back over one thousand times.

Heavy.

I think an effective way of describing the dynamic qualities of the chromosome is to use a few metaphors. My older daughter likes to knit, so we often visit the knitting supply shop in town for fresh yarn. Yarn usually comes wrapped in skeins, a length of yarn wound around a reel. Most yarn comes in lengths of 80-150 yards. One of the nice things about buying yarn this way, rather than just as one long unwound string, is that you can put it under your arm and walk to the car. This is certainly better than tying a knot to the rear bumper and pulled the unwound string all the way home. Thus, the first important lesion of chromosome dynamics; if you’re going to reproduce you’ve got to stuff that entire DNA into a very small, tight package. Chromosomes are just that: tight packages of DNA.

On the other hand, it is very difficult, if not downright impossible to knit anything if the skein of yarn still has the paper label wrapped around it. In order to use the yarn, you have to unwind it. That’s the formula: when the cell needs to use DNA to get information about how to make a protein, it has to unwind it. When it needs to reproduce, or turn off the DNA information flow, it needs to concentrate and condense it.

How this occurs is rather wondrous, and will be the subject of much discussion later on when we talk about how you can modify your genetic destiny, but for now we’ll just stick to the basics. DNA is packaged and concentrated by special proteins termed histones. This concentrated DNA is called chromatin, which is the DNA plus the histones that package DNA within the cell nucleus. Chromatin structure is also relevant to DNA replication and DNA repair.

Histones are very cool bead-like proteins that spool the DNA in a way that makes it either tighter or looser, sort of like the cardboard around which our skein of yarn is wrapped. Histones respond to changes in their structure by tightening the DNA wrap or loosening it. Whenever a cell needs to access the genetic information encoded in its DNA, the histones on the section of the DNA that is needed undergo a chemical reaction called acetylation by which a molecule called an acetyl group is stuck on the histones, causing them to relax and unravel. When business is concluded for the day, special enzymes come along and chomp off the acetyl group cause the histones to become de-acetylated, which makes them tighten up again, sending the DNA in the region back to its resting state. Think of it like this; when your DNA needs to work its histones chow down on acetyl groups for breakfast and they do yoga; when it needs to reproduce or shut down, the histones lift weights --the strain of which causes the acetyl group to pop out of their mouths.

Make sure that you’ve mastered the last paragraph, because much of the very cool stuff dealing with how you can modify gene functions pretty much requires that you know this stuff. By the way, this is very, very cutting edge material; only until recent times have we understood this mechanism, and of supremely paramount importance, that it is used by the environment to influence gene function and that influence, for either good or bad, can be passed on as inheritance.

Scientists have given each human chromosome a number, according to its size; thus chromosome number 1 is the largest, then number 2, etc. Chromosomes come in pairs, one from each parent. So there are 23 pairs, for a total of 46 in us humans. Numbers 1-22 are non-sex chromosomes called autosomes, and pair 23 contains the X and Y sex chromosomes.

In the few minutes it has taken to read up to here, this, around 400 million of your red blood cells were depleted and replaced, consistent with the set of genetic instructions contained in your DNA.

One of the features that can be of most use when GenoTyping someone is actually one of the hardest to come by: Getting the ABO blood groups of your parents.

Its importance should come as no surprise, since epigenetic changes are largely influenced by the patterns of gene activation and silencing that occur as part of

• The heritable epigenetic component (you start off with the patterns of gene expression that your parents give you)
• The prenatal environment (there are two major bursts of methylation activity in the fetus: at about 8-12 weeks, then again in the last trimester)
• The immediate postnatal environment (these are mostly related to gene expression due to hormones such as growth factors)

In fact one of the studies that got me interested in the largely unrecognized effects of blood groups as a modulator of the epigenetic environment was a study that looked at childhood ear infections and blood groups. However, unlike most epidemiologic correlation type studies, this one looked at the blood group of the child’s mother.

Maternal blood group A gave a relative risk (RR) for intervention of 2.82. The noted occurrence of an attack of acute otitis media (AOM) before the first birthday gave a RR of 6.13. When these two factors were used together, the RR climbed steeply to 26.77.

Now to understand just how strong this association is we should look at exactly what a RR (relative risk) is. Basically it is just the odds (over 1) that something will occur over it being random. An RR of 2 (about the RR of elevated cholesterol causing a heart attack) means that people with elevated cholesterol are twice as likely to get a heart attack as people whose cholesterol levels are more desirable. Thus the study is saying that if you are a kid with an ear infection in the first year of life, and you mother is blood group A, you are 26 times more likely to have a recurrence.

Here is a chart I made which compares relative risks for several common problems and factors associated with that risk. Obviously, this is a very strong association.

Are the effects of having a blood group A mother and getting ear infections the result of some sort of fetal programming? We know that some studies have linked the ABO antigens to cellular differentiation (the process where developing cells move from general embryonic 'germ' types to cells with more specific functions, like a pancreatic or epidermis cell.)

ABH antigen expression was considered as suggestive evidence for the assumption that blood group antigens could serve as early immunomorphologic markers of endothelial differentiation of mesenchymal cells, thus specifying the location of future blood vessels. Extending the conceptual framework of blood group antigens' significance we consider them as being possibly involved in the process of fetal morphogenesis.

In epigenetic terms, we may wind up being more interested in your parent's blood types are that perhaps we need be with yours.

Every once in a while, amid the junk mail, bills and catalogs, I receive a letter which surpasses all prior. In a wonderfully sycophantic endeavor this gentleman writes to ask me for a complete set of my works so he can continue on his mission to educate the Indian public about healthy living. Apparently the gentleman does it free of charge.

Sir, your books are on their way.