Fig. 2

Primers and PCR reactions for allelic genotyping of an L1 element (a) and standard gel electrophoresis analysis of the E and G reaction products (b). a: The E reaction uses primers located in each of the L1 flanks and tests for the presence of an allele without the L1 insertion. The G reaction uses an L1-specific primer and the primer in the 3’ flank and tests for the presence of an allele bearing the L1 insertion. Primers used in the first PCR (red) are tailed (SP1 and SP2 sequences) so that the adapter (P5 and P7) and index sequences can be added in a second round PCR (green primers). b: Three possible diallelic genotypes based on the presence or absence of the E and G reaction products on an electrophoresis gel. Black filled and empty boxes represent respectively, the presence and absence of a PCR product. The gray filled boxes (marked with an asterisk) represent the (longer) product from the E reaction that is generated in the presence of an allele bearing a short L1 insertion