Biology Project: Tetrapod Limbs & Polydactylism. Help?

Question

For my biology project i'm researching polydactylism which is when you have more than 5 fingers/toes per hand/foot. One of my questions is How can a mutation result in an added structure, such as an extra finger or toe? (hint: research the genetics of the tetrapodlimb)

and im having a real hard time finding sites that talk about that on google/yahoo. either its like too complicated for me, or it doesn't even include what im asking for. any sites that could be useful or helpful would be great. or if you just know the answer that'd be great too ! any help will do. thanks :)

Haha. This is not a university class. i'm a freshman. honors biology. :P

^ As I said above, this is not a university class but it's not as hard as you may think it is. I have to research 2 inherited traits and 2 non inherited traits out of several given for my project.
So i chose polydactylism, the basic info is easy : dominant/recessive, autosomal/sex linked, what chromsome. it was just theres two questions and that one question i dont understand. but thanks everyone for yourhelp :)

Answer 1

No problem! See below.

Answer 2

What level of course is asking you this? Researching the genetics of tetrapod limb development is I hope university level.

The material I found is, as you put it, complicated. But we are talking about how genes regulate the formation of structure, here, and not just in general terms, but in a specific case.

I looked up the first tetrapod limbs, evolved from the lobe-fins of the Sarcopterygii. The restriction to five digits appears very early in terrestrial vertebrate history. The paper I found not only discusses this "bau-plan" for forming digits in tetrapods, but discusses what genes are involved - genes that we still carry, and gives diagrams (like p.6) of where in an embryonic limb bud they are expressed, and what the resulting bones look like.

A direct link of genetics to anatomy! You may have to spend some time interpreting and simplifying their findings for your own purposes, though.

The Sarcopterygians likely had many rows of bones in their lobe-fins, and the genes regulating or reducing this for tetrapods still exist in us. Read up on which genes here do what, and you may get an idea of a change that could happen with one of these genes to allow sixth digits to grow.

Good luck!

Answer 3

PubMed is where you want to go - here, for instance is an article that may be useful, along with a set of links to other, similar articles. These may well be a bit beyond your present level of study, but I bet you can pull out the key ideas and look up what is not clear to you at first. I hope this helps!

http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1594969