|MadSci Network: Biochemistry|
First of all remember that the things you eat were all living at one time. And since they were living things, composed of cells, they must have their own DNA. So when you eat anything, you're eating it's DNA too. THIS IS NOT SOMETHING TO BE WORRIED ABOUT THOUGH! What happens is that the DNA gets broken down into single nucleotides in your digestive tract. This is just like proteins being broken down into amino acids. There are cells in your intestine that can take up these free nucleic acids, and pass them into the blood stream where other cells will take them up, and use the nucleotides to make new DNA. The other thing that your body can do is to make its own nucleotides from scratch, using the sugar ribose, phosphate, and the amino acid aspartate and other small molecules to make the bases. Making nucleic acids requires specific enzymes in your cells.
The answer to your question about foods moms eat while pregnant, is yes. Growing fetuses get all of their nutrients from the moms...either in the form of already made nucleic acids, or the building blocks to make them from scratch.
The other thing to think about in terms of eating, is that there are specific ways to damage your DNA. One non-food example of this is UV-damage to DNA, like from the sun. In terms of nutrients which can damage DNA, there are some very common nutrients which the body absolutely needs, but having too much of them can cause damage to DNA. Some of these include iron, and vitamins E and A. DON'T BE ALARMED BY THIS, AND BY ALL MEANS DON'T STOP EATING THINGS WHICH ARE GOOD SOURCES OF IRON AND VITAMINS, because your body really does need them to do good things.
A couple websites I found useful in answering this question are:
This talks a lot about the organic chemistry of making nucleotides, and might be a little hard to understand.
http://vector.cshl.org/dnaftb/ Is an interesting site about all kinds of aspects of DNA, especially genetics of DNA and stuff.
If my answers aren't clear, ask more questions!
Good luck with your science class!
Try the links in the MadSci Library for more information on Biochemistry.