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[quadir]

i have got an assignment which requires information
about how cells mutate and why and how these
mutations occur. any help would be welcomed!

[MayoFlyFarmer]

I'm sure you know this naked (and good overview by the way, I'm sure that helped quadir out a lot) but I want to bring up on key point for others who might read this that you left out, and frankly a lot of people leave out of the story.  Cells don't even have to have a change in their DNA to induce a change in their function.  Environmental factors (whether from sources outside the body, put into the body, or chemicals excreted by neighboring cells).  Remember that all your cells have an IDENTICAL copy of your DNA.  They obviously do not all express everything that is encoded into that DNA though.  If they did, and you had blue eyes, the fat cells in your butt would excrete the same blue pigments found in your eyes, and you'd have a blue butt too.  As a matter of fact every cell in your body would be identical.  So ontop of the actual genes encoded in your DNA there are also many elements that regulate which of these codes will be read (transcription factors).  These factors can be influenced dirrectly by external cues, and can thus change the activity of a cell with no actual change in DNA.  
Like I said before, I know that this doesn't dirrectly relate to the actual question (but its a neat side point) and most people on this site already know about it.  But we get so worked up about the genes coded in our DNA that we over look TF's quite often so its good to remind ourselves about them

Yar, the flies be everywhere!!!

[ebzZzZ]

who says cells can't change their DNA? adaptive mutation in
bacteria says they can.

all you need to do is look at the fruit fly used in research
to see that there is far more involved than random mutation
of genes

[ebzZzZ]

who says cells can't change their DNA? adaptive mutation in
bacteria says they can.

all you need to do is look at the fruit fly used in research
to see that there is far more involved than random mutation
of genes

[alastair84]

I thought ALL mutations were random. Am i wrong? If I am right, you cannot possibly say that cells "control" DNA? Cells may be able to control what genes are expressed, but i thought that since mutations are random, it's just like saying we control the throw of a die.

[MayoFlyFarmer]

quote:Originally posted by alastair84

I thought ALL mutations were random. Am i wrong? If I am right, you cannot possibly say that cells "control" DNA? Cells may be able to control what genes are expressed, but i thought that since mutations are random, it's just like saying we control the throw of a die.

a mutation by definition is not neccisarily random.  it just means a change in code.  If I purposely changed a T to a G  thats would still be a mutation, but it cn not be considered random.  HOwvere, getting to the point that you were talking about, most mutations in nature are random (at least to some degree... a point mutation is more random than a translocation etc.)  and they DO happen randomly.  But the don't have to HAPPEN randomly.  Many bacteria and other cells possess the ability to cause conditions withinthemselves that favor mutations often while under some sort of stress.  the hope being that they will by chance mutate to a form that is better fitted to the current conditions.  So while the actual mutation in that case is random, the fact that it happened isn't.  To use your example, while I can't control what the dice land on, I can control whether or not I throw them.  Although from time to time I may drop them even when I mean to hang on to them.  Also in refference to different types of mutations, I can throw a 6 sided die or a96 sided die.  odds are a little different

That's no moon.... its a GRAPEFRUIT!!!!

[MayoFlyFarmer]

Awe, geeze you're calling my bluff eh?  :)
Its been about 4 years since micro, and 2 since molecular, but I remember learning about these phenomena in both (especially micro)  If work ever clams down (so never) I'll dry to dig out the old info for ya

That's no moon.... its a GRAPEFRUIT!!!!