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Hi!  Dr. Pat
Is DNA only found in living things?


  HI Al!,
The simple answer is yes.

Things that are not and never were alive (rocks, cars, or lollypops for instance) do not have DNA.

DNA is made by living things and is found in living things. Once those animals and plants and such die, you can still find their DNA if the conditions are right. For instance, you can pick an onion and keep it in proper storage for months and still get some DNA out of it. But, store it poorly and the whole thing will rot, including the DNA. The whole Jurassic Park movie was based on the idea that prehistoric animal DNA was "properly" stored in amber and thus, the creatures could be cloned back into existence.

And, forensically speaking, one can find DNA wherever a living thing has left some behind. Humans leave their DNA all over the place. Whenever you shed skin or hair or saliva (cheek cells will be in the saliva), your DNA can be found. If you lick a stamp, you may very well leave enough DNA behind for the forensic experts to say it was you who licked the stamp.
Dr. Pat

Dr. Pat
About how many DNA strands make up the average human body?
Dr. Smith

  Dear Dr. Smith,
Interesting question, and one you would think could have a straight-forward answer. But, alas, not so.

The best I can find, there are 'trillions' of cells in the human body. There are 23 pairs of chromosomes, or 46 strands of DNA per cell (not counting eggs and sperm). So generally speaking there would be more than
46, 000,000,000,000ish strands of DNA in the human body. But, that is if you ignore the DNA in mitochondria. I have no estimate of the number of mitochondria per human body and do know that the number per cell fluctuates wildly between cell types.

There is an intriguing estimate of the length of DNA in the human body. If all the DNA from an average person is laid end to end, it would stretch from here to the sun, and back, 30 times.

Thanks for your question.
Dr. Pat

Do you have info on the human genome project?  If not do you know where I can get some?  I would be very grateful.
Thanks, Miranda

 Hello Miranda,
Here are two sites from which you can get not only a lot of information, but also many more links to the human genome project.

The first is probably easier to understand.

And the second is the government's main site for the project.

Good luck.
Dr. Pat

My 5th grade daughter has to make a model of a plant or animal cell for her science class. The teacher recommended this site. However, I cannot seem to find an actual cell of a plant or animal just descriptions of them. Does this site have actual pictures of a plant or animal cell?  If not, do you know of a site that might have pictures so that she can make a model. Thank you!

 Hello Chris,
A very good site is

Good luck to you daughter on her project.
Dr. Pat

Hi !
I have a project due and I need to know what an animal cell's purpose is.  HELP !!! HELP !!!

 Hi Jennifer,
That is a difficult question.  There are many different 'kinds' of animal cells that each fulfill a different function.  For instance, a skin cell provides a protective layer from the environment to the rest of the body -- the red blood cell carries oxygen around the body so that all cells may stay alive -- the muscle cell can contract so that the whole muscle pulls or pushes on something and the body becomes mobile that way.  So, each animal cell does a specialized job that all adds up to the whole animal breathing, eating, walking, (and in some cases talking on cell phones) and going about the world being the animal.
Dr. Pat



 Learn more! Google:
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