I did do school biology, but...

June 27, 2010 2:36 PM

Pretty much every cell in a organism contains the DNA for that whole organism. How does a mutation in one cell pass on so that it becomes part of the DNA of every cell or actually affects a characteristic in that organism or its child?
posted by westerly to science & nature (6 answers total)

Mutations only affect children if they happen in sperm or eggs
posted by mpls2 at 2:39 PM on June 27, 2010

Because each (sexually reproducing) organism starts out as just two cells, a sperm and an egg. So if I am irradiated and a spot mutation affects my sperm (or affects my reproductive organs in such a way as to make them produce nonstandard sperm), then that mutation will naturally spread to the entire organism that is my child.
posted by 256 at 2:39 PM on June 27, 2010

1) Germ line cell (as people are mentioning above, sperm or egg has the mutation)

2) a stem cell acquires a mutation and divides...and passes on those genes to the new cells that divide from this cell. This is how cancer begins (not just one mutation, but several mutations...and the mutations often prevent programmed cell death (apoptosis) or promote cell division, etc.).

Also, just a note...all cells will not contain DNA. Red blood cells, for examples, are enucleated during development. There are a few other examples similar to this
posted by Wolfster at 2:44 PM on June 27, 2010

Mutations can also happen in somatic (non-germline; not sperm- or ovum-producing cells)--either through random accidents in the typical function of the cell, or by some sort of external event such as exposure to radiation or mutagenic chemicals.

In this case there are a number of different possibilities, depending on luck of the draw, more or less--where in the genome the damage occurs, whether it's repaired:

--There may be no effect--cells can repair damaged DNA in many cases.

--There may be a strictly local effect, i.e., the lone affected cell is altered in its function in some minor way.

--There may be a bigger, but still localized effect, like tumor formation, or minor alteration in some biochemical system.

--Or there may be an effect across the entire organism, like metastasized cancer or a major biochemical system alteration.
posted by Sublimity at 2:46 PM on June 27, 2010

The basic mechanism here is cell division, new cells come from the splitting up of older cells and any changes in DNA can only be carried into the new cells, not go backwards to the older ones.

Another thing to keep in mind is that not only does an embryo start from a single cell (made by the fusion of two germ cells) which then divides to form all the other cells but the split into somatic cells (the ones that become you) and germ line cells (the ones that make sperm or eggs and become your child) happens at some point during development. So if the mutation happens before that split then it may end up in both somatic and germ cells, so ends up in both you and your child.

As an adult most cells either don't divide any more or only divide a few times. Stem cells are able to keep dividing and replenish other cell populations so if you get a mutation in one of those it will generally have a larger effect than on in a terminally differentiated cell (one which has reached its adult form and stopped dividing). So the spread of the change will depend on what kind of cell it happens in. But then there's cancer, where a mutation makes a cell start dividing again, often rapidly and aggressively, so that damaged cells makes a whole lot more of itself spreading it's mutations into all the daughter cells. That can have quite an effect on the organism's characteristics.

What happens in probably the majority of the cases where a mutation makes a change to a cell is the cell dies (apoptosis). Add in the DNA repair mechanisms to prevent the change from sticking and there are pretty decent mechanisms in place to stop DNA changes from happening.

Then when you add in epigenetics (genes being turned on and off without changing their sequence) it gets really messy :-D
posted by shelleycat at 4:21 PM on June 27, 2010

I'm not an expert but I think one important point is that generally, it doesn't. A DNA variation can result in an cancer in an individual but (thankfully) it would take a DNA variation specifically in the sperm or egg to create problems with the child. Of course when you mix DNA from a sperm and egg, you are creating variation inherently, but if one of the organisms has a cancer somewhere on its body that is a variation from its fundamental DNA, that will not be passed on.

However I don't know what I'm talking about, so forget that.
posted by sully75 at 7:30 PM on June 27, 2010