I’m being asked a question I’m not sure how to answer. This website: http://www.thelocal.se/20336/20090629/ says that they are finding that DNA changes as a result of C-sections. My understanding would be that it would be as the result of trauma. The moms on a mailing list I’m on don’t understand how DNA can change. My understanding is that DNA can be damaged and damage is change. Am I wrong? I have found a variety of other articles documenting DNA change after trauma but I guess I’m just not explaining it well?
DNA can be damaged, yes. It’s often a precursor to cancer of various kinds. Changing of DNA in a way that persists in a full-body way in cells not directly involved in the trauma is more unusual, I believe.
There are other ways *that* can change, too, of course. The most common that I know of is retroviruses — viruses that alter DNA.
The DNA of some cells is being affected, but those mutations aren’t likely to become heritable.
In all probablity, lots of your cells have mutations (changes in DNA) from various causes. It’s only mutations in the germ cells which are heritable.
I can’t find an article about this in PubMed, which always raises eyebrows when this kind of thing is reported via popular media. There are a lot of articles in PubMed about the link between caesarean delivery and allergy/asthma, though. Not sure if there is a causative link, and it’s very controversial, but people are looking.
Our immune cells are always undergoing genetic changes; it’s part of how they get programmed for specific tasks. It’s possible that this is poorly understood by the reporter**, and the changes being described are those of immune cells undergoing a response to stress. Things like adrenaline will cause changes in immune response. That’s generally a good thing. Because babies are in the “programming” stage of their immune system, it’s possible that this early stress event could have later repercussions.
But lines like “different DNA sequences” throws up my red flags for being nonspecific, and probably incorrect. Evidenced by your mailing list, poor reporting like this leads the general public to think that general changes in DNA sequence are taking place when that is probably pretty far from the truth. Also, this sentence: “The researchers noted differences in DNA sequencing of babies delivered via Caesarean and those delivered normally…” doesn’t even make sense. Sequencing is a process, not a read-out. Perhaps they meant “DNA sequences”, but the lack of attentiveness to this kind of detail makes the whole article suspect. Gah.
…All of this is different from DNA damage, which yes, can happen, and yes, is a change. Our cells are WELL equipped to deal with most types of damage, and even the occasional cancerous cell is usually killed by our immune system. But in the case of too much sun exposure, for example, the accumulated damage over time overwhelms our cells’ capacity for repair and/or increases the likelihood of a malignant growth getting missed by our immune systems. Alternatively, oncogenic sequences can get swapped into different parts of our genome and start being expressed where they wouldn’t otherwise be expressed, another form of damage which leads to cancer. Lots of different ways for damage to happen (some of it is even intentional, such as in certain immune cells). Lots of ways for it to get repaired. Lots of possible outcomes.
**Yeah, not understood. I just found this:
http://www.medscape.com/viewarticle/705279
Methylation is one of the ways immune cells are programmed for function; it doesn’t actually change DNA sequence though (hence the term “epigenetic”). It would be interesting if they can show something causative but my suspicion is that it’s far from proven. And I could probably dive head-first into the science but have to get back to work…
Hope this comment makes a shred of sense!
http://www.genetichealth.com/g101_changes_in_dna.shtml
See the second section in particular.
What I was able to figure out…
DNA can unequivocally change (e.g. retroviruses), but in this case one can argue about whether one would say the DNA is changing here. The changes this group found (according to http://www.physorg.com/news165508836.html) are a process called DNA methylation (http://en.wikipedia.org/wiki/DNA_methylation) which does change the DNA molecule but which does not change what we usually call the “DNA code”, the latter meaning the sequence of A’s, T’s, C’s and G’s.
It’s more like … it’s more like you can stick little methyl post-it notes on the DNA sequence that say “don’t express this” on a gene (a sequence of those A’s, T’s, etc.), the post-it essentially inhibiting whether (or how often?) that sequence gets turned into a protein that runs off and does something in the body.
Is it change? Certainly.
Does it change the genetic code? Kinda depends on which flavor of pedantry you use for the words. It doesn’t change the sequence of A’s, T’s, etc., but it does still little chemical markers onto those letters which have the result of changing how often that genetic software is run.
Is it damage? Again, pedantry: I think of damage as “change with a negative value judgment.” DNA methylation isn’t (as I’m reading it) always a bad thing, so I’m not sure I’d always call DNA methylation “genetic damage”, but I can see where people would think of a change that caused, say, “immune system problems” as damage.
Just to connect this all up: This would be an example of the “DNA expression mutation” at the bottom of the page linked to.
Err, one more detail. The post-it-notes do get copied when DNA is replicated, so these changes can be inherited.
I wonder how this affects c-section deliveries that take place after an attempt at vaginal birth (w/ or w/o epidural).