Figure 2.

Human diversity associated with a long L1Hs Ta insertion polymorphism, as shown by an agarose gel chromatograph of the PCR products from a survey of the human genomic variation associated with L1HS364. Because of the size (∼6,000 bp) of this L1 element, two separate PCRs are performed to genotype individual samples. In the first reaction, flanking unique sequence primers were used to genotype the empty alleles (A); amplification of empty alleles from this locus generates a 97-bp PCR product. In the second reaction, a Ta subfamily–specific internal primer termed “ACA” and the 3′ flanking unique sequence primer were used to genotype filled sites (B); the amplification of filled sites generates a 170-bp product. In this survey of human genomic variation, 20 individuals from each of four diverse populations were assayed for the presence or absence of the L1 element, with only the Egyptian samples shown here; the control samples (black lines) were TLE buffer, common chimpanzee, gorilla, and owl monkey DNA templates. This particular L1 insertion polymorphism is a high-frequency insertion polymorphism, and most of the individuals surveyed have L1 filled chromosomes.