Question

Why is it necessary to use different primer sets for different species to amplify the same gene?

Answer 1

I am sure you are aware that primers actually are used for specific target amplification. You might argue that DNA polymerases can do same function as a primer howerver, DNA polymerase can only add nucleotides to the pre-exisiting DNA molecule and thats why a primer is requires. As a specific pair of primer can be used to amplify any specific DNA sequence. Therfore, primers have to be designed based on the specific DNA sequence inorder to anneal with during PCR. To conclude, primer specificity depends on the complimentary target sequence and as a result there is the neccessity for different primer sets for different species even though you need to amplify the same gene.