The DNA is homogenous through-out the entire body of the fish (or all creatures for that matter). What you should be asking is 'which part of the fish's genome do you mix with your own DNA to become...
you need help. HELP YOU!! Leave the fish alone
ew...why would u switch dna with a fish? just use a spell or get a witch to do one for you. either that or have a mermaid give u their tail but not...
No. I suppose at some point in your life you must have eaten fish of some sort. A fish stick at school or your dad caught trout that you had for dinner. You ate it and did you turn into a mermaid...