Why can the polymerase chain reaction only be used to amplify genes that have...

[quicksilver4648]

...been cloned and sequenced? The polymerase chain reaction can only be used to amplify genes that have already been cloned and sequenced. Why is this true?

[Warthaug]

Its not entirely true.

Generally speaking, you need the gene sequence so you can design primers which will recognise the gene of interest. Since this requires you know the gene sequence, to design those primers.

However, you can use random hexomers as primers, to randomly amplify cDNAs. This amplifies all of the cDNAs in a sample, but in theory you can pull out your gene of interest.

Bryan