A DIMORPHIC ALU SB-LIKE INSERTION IN COL3A1 IS ETHNIC-SPECIFIC

Alu elements are a class of repetitive DNA sequences found throughout the human genome that are thought to be duplicated via an RNA intermed iate in a process termed retroposition. Recently inserted Alu elements are closely related, suggesting that they are derived from a single s ource gene or closely related source genes. Analysis of the type III c ollagen gene (COL3A1) revealed a polymorphic Alu insertion in intron 8 of the gene, The Alu insertion in the COL3A1 gene had a high degree o f nucleotide identity to the Sb family of Alu elements, a family of ol der Alu elements. The Alu sequence was less similar to the consensus s equence for the PV or Sb2 subfamilies, subfamilies of recently inserte d Alu elements, These data support the observations that at least thre e source genes are active in the human genome, one of which is distinc t from the PV and Sb2 subfamilies and predates either of these two sub families. Appearance of the Alu insertion in different ethnic populati ons suggests that the insertion may have occurred in the last 100,000 years. This Alu insert should be a useful marker for population studie s and for marking COL3A1 alleles.