Okay, I tried searching for a topic like this and I came up with blanks. I think I posted this in the right section, but you never know, so bear with me.

1. In Harry Potter and the Deathly Hallows - When Ron takes the Polyjuice Potion (PP) and transforms into Harry (in the beginning) and looks at his chest. He makes a comment similar to "I knew Ginny was lying about that tattoo." If there was a tattoo in question, would it show up? The way I understood it, you transform into someone else by drinking the PP only if you have a piece of them. (Hair, toenail, you get the idea.) Well I thought that you are basically taking a piece of their DNA, so when you transform, you transform into what the person originally looks like. I mean Harry wasn't born with a tattoo, so a tattoo wouldn't show up, would it? (I know he probably never actually had a tattoo, but you get my point.) Like if you transform into someone who had brown hair but dyed it red, you would transform and get their brown hair, right? Just wondering...

2. When you drink the PP, you just gain the person's appearance and voice. You don't get their personality or their mind. If you drank the PP, and ate a whole lot of food for a month (while still remaining that person), you would imagine you would appear fat, correct? So say you go back to your usual self, would YOU still be fat? Same goes for if you got a tattoo or dyed your hair or got a bruise or any other physical appearance while you were the other person.

3. This might be a little confusing, so hang in there alright? Imagine someone took clippings of your hair while you were a baby and put the hairs in a safe place. So you grow up and several years later you find you need to go back to your younger self. Miraculously, someone (for no apparent reason) had taken clippings of your hair when you were a baby. So you put YOUR OWN BABY hairs into the PP. Would it work like that? Could you transform back into yourself, as a baby? Or simply a younger self? It seems odd it would work that way, so would it?

Thank you for bearing with me. Some of the questions may have seemed silly, confusing, simple, obvious, or just plain strange, but sometimes I'm that way... Please give me your opinions!

but, when the had polyjuice potion, they had the lightning scar didn't they? and he wasn't born with that, I believe that it just makes you a temp. copy of the orginal at the time they hair/piece of DNA was found.

Hope I helped!!

The first two I think it depends on what part of life you are. However, your third question is something. If someone drank the PP with the baby hair, then they would turn into a baby, I believe. However drinking your own baby hair with the PP, I don't know if it could have an effect on you. I will do this for you, though. I have a Harry Potter club on my campus and I will ask your last question to them for we discussed the others ones before.

Apart from these questions I have one particular mind-boggling thought/question. You know in the COS the PP turned a certain color according to the person. Crabbe and Goyles were merky and filthy brown and green looking. Then in Deathly Hallows, Harry's PP color was gold. Do you think the PP's tell a person's personality by a color. If so, I wonder what my PP color would be? They should have quiz for that one day.

To answer both of your questions, I think the answer is that it's simply magic. It don't think it's a question of DNA or science, but that the hair is only necessary to identify which body you'll be transforming into, and then magic does the rest and makes you look like the person looks at that moment. But your second question is particularly interesting... I don't know, I really don't. My guess is that they would turn into a baby, but that doesn't really fit with everything else I said...

AryaForce that's so very true! They have all the animagus/patronus/etc quizzes, so maybe they should open a Polyjuice one!

All right here is the response to your third question from my Harry Potter club. They believe it could be possible to turn into your baby self. However they feel that using it on yourself would be inconsistent. They were apply all of this to Moody and his chunks of hair not being on Barty Crouch Jr. when he continued taking the PP through the fourth year. Something to think about, at least. I didn't get it.