Re: Human Alu PCR Lab Report (200Pt. Due 4/15)

Re: Human Alu PCR Lab Report (200Pt. Due 4/15)

Introduction The Alu element is actually a family of DNA sequences found only in primate genomes. (Dolan, 2001) There 14 known families of the Alu element and the family relationship are based on the gene sequence similarity. (Russel 1998) All 14 families are present in the human genome. The more recently evolved the organism, the more different variations of the Alu element will be present. Alu insertion polymorphism is autosomal markers that reflect both the maternal and paternal history of a population (Nasidze, 2001). They are stable markers that reflect unique evolutionary events. Alu element is a type of gene known as a polymorphic transposon. In humans there are over 1.5 million copies of the 14 subfamilies of the Alu gene with the average similarity being between 85% and 98 % (Makalowski, 1995). The transposon is flanked by inverted short terminal repeats and encode for the protein transposase which allow the gene to be inserted into the DNA (Makalowski, 1995). How an Alu element transposes: (Dolan, 2001)-First, the inserted Alu is transcribed into messenger RNA by the cellular RNA polymerase. -Then, the mRNA is converted to a double-stranded DNA molecule by reverse transcriptase. -Finally, the DNA copy of Alu is integrated into a new chromosomal locus at the site of a single- or double-stranded break. The Alu element is considered to be a class of mobile elements known as Short Interspersed Elements (Nasidze, 2001). The elements are usually about 300 base-pairs in length and are interspersed throughout the genome. For a long period it was though that the Alu element had no function at all and the true function is still unknown. Alu rarely transposes itself into regions critical for DNA function where it would possibly corrupt the code. This leads to the conclusion that the Alu gene family has the ability to modify gene for a genetic advantage. The Alu family of genes may be involved in regulating mutations to deal with stress. (Chu et al, 1998). Most Alu have both of the paired chromosomes with an insertion at the same position. However, many Alu insertion can be dimorphic, meaning that an insertion may be present or absent on each paired chromosome (Dr. Lin’s notes, 2003).