Germline cells are immortal, in the sense that they can reproduce indefinitely. This is largely due to the activity of the enzyme known as telomerase. This enzyme extends the telomeres of the chromosome, preventing chromosome fusions and other negative effects of shortened telomeres. Somatic cells, by comparison, can only divide around 30-50 times due to the Hayflick limit.That little tid-bit I found rather interesting for several other reasons...
Changes in the DNA due to Diabetes
That article is an example of a change occuring through 'natural causes', however, by using retro-viral vectors that infect a wide range of cells in a wide range of tissue types, changes are theoretically possible as well. Problem is, most such vectors target fairly specific cell types.
Retrovirus vectors are the agent most commonly used to insert, or change, genes in multi-cellular organisms. They are the agent used for the retroviral based flu vaccine. Also, there have been some other gene therapies developed on retroviral vectors. The problem with them, as disease treatment agents, is that they are finite; that is, the immune system eventually clears them, and any cells with altered DNA are eventually lost due to normal tissue turn over. So, the "cure" is not permanent.
And, of course, mutagens can impact and alter DNA on a cell by cell basis. And, several environmental toxicants are now known to exert an "epigenetic" effect on DNA. Exposure to these after birth leads, especially during early development, to a change in DNA structure in many or all cells. The change is not a mutation. Rather, it is a change in DNA methylation or histone phosphorylation, that alters gene expression. This epigenetic mechanism is now recognized as one of the primary ways that environmental substances may cause disease later in life.
The field of molecular biology and genetic engineering began in the 1970's with the discovery of restriction enzymes. The structure of DNA was understood. From the 1970's, our ability to manipulate DNA has exploded as we have developed an ever increasing repertoire of tools with which to manipulate DNA, and as we have elucidated the sequence of the human genome.
Seldom a week goes by without the discovery of a gene for yet another disease. Genetic explanations are touted for everything from cancer and heart disease to more diffuse conditions like alcoholism, homosexuality, and crime. It's been suggested that there may even be a gene for shyness! Biologists believe that new gene technology will revolutionize our understanding of disease and will have a greater impact on us than nuclear power or the computer.
What will make an even greater impact, however is the discovery of being able to alter these markers and genes which create traits such as shyness. What will we be when we can alter our base personality? What happens when the effect wears off?
