Learn more about these interesting structures by visiting the bottom of the page containing photomicrographs.
Sometimes scientists get very polarized, just like politicians. For example, were the dinosaurs killed by an asteroid, volcanoes, or disease? Well, it could have been all three and then some, via a cascade. First the asteroid hits. This sets off the volcanoes. The forests all burn up, reducing oxygen levels from 30% to around present day levels. The dinosaurs get sick and succumb to diseases. The larger ones can’t handle the low oxygen levels. You get the picture..
Keeping this in mind, let’s take a look at stem cells and differentiation. On the one hand, there is the mindset that DNA is “immutable” when it comes to differentiation, i.e., except for mutations, DNA doesn’t change as cells differentiate. Perhaps it gets inactivated by heterochromatin or some other kinds of protein suppressors. This is certainly a valid argument. Furthermore, the DNA is assumed to be linear in structure because chromosomes are basically linear, genetic recombination can be accurately interpreted using a linear map, and when DNA is fragmented the linear pieces can be made to line up to fit this recombination map.
However, one must somehow come to terms with the photomicrographs shown on this blog which seem to “fly in the face” of this simple linear chromosomal model. These photomicrographs would be better explained in terms of recombination events that occur during the differentation of lymphocytes in which circles of DNA are released during immunoglobulin gene rearrangements resulting in a permanent change in the structure of the DNA. So the question that remains is simply which model is correct: Permanent stability or permanent change? Again, let me refer back to the dinosaur extinction. Both models could be correct. How? It is well known that DNA exists as compartments within the nucleus. There is no reason why one compartment couldn’t be permanently altered while the others remain bound up, inactive, and untouched. When adult cells are converted into “stem” cells by artificial means, the active compartment may become inactivated by binding it back up; even though genetic rearrangements have already occurred. Another compartment could then be released and permanently altered prior to gene activation. Does this actually happen? There is only one way to know. Please read on..
I am looking for a lab that works with in situ gene hybridization and immunofluoresence to engage in a pilot study. I would like to see where particular genes of interest are located within the circular structures shown on this blog. I may be contacted at firstname.lastname@example.org.