Epigenetics and missing parts: The making of the Homo sapiens machine

Who would have thought? We are not exactly what our genes say we are...

As you know, we have tow sets of chromosomes. One of paternal origin and the other, well, from our mom! Genetic traits are transmitted from generation to generation and this long nose of yours is probably found in some of your family members. It has been found that we are more than that. In fact, tiny modifications on your DNA control the way the genes are turned on...or off! In plants, environmental stress on a generation can modify the expression of some genes in the next. How can stress affect the way the next generation behaves. Is that possible in humans? Some think it is. Stress, nutrition and possibly other factors can influence the way our DNA is expressed. Thses factors modify DNA structure by adding methyl groups (-CH3) here and there. These modifications, leave the sequence intact and can be passed to the next generation. These modifications can either activate or inhibit gene expression.

Ragarding stress, an important and interesting experiment is taking place. Dr. Rachel Yehuda, a specialist of posttraumatic stress disorder, is following the offspring of women working at or at close proximity of the WTC towers. In one of their studies, they found that head circumference was decreased in infants born from these mothers. In the years to come, the children will be followed for neurological development. Some researchers have found that malnutrition of an expecting mother can increase her offsprings chances to develop diabetes stroke and even heart disease later in life...you see, we are not what our genes say we are.

Furthermore, it is known that our individual DNA is different from other individual. We might share 99.9% of the DNA sequences, there are many spots where these sequences are different. These differences help pharmaceutical companies to understand why some people are fast or slow drug metabolizers. It helps police to identify criminals that leave biological tracks and help body identification when disaster strikes. It now seems that there are more differences in our DNA than previously thought. In the latest Nature issue (23 november 2006), researchers demonstrated that genetic variation within individuals is more complex than previously assessed. In some cases, whole sequences were deleted.