with a lower accuracy. It includes RAPD, RFLP, AFLP and so on. Cosmid/BAC/YAC end sequences Cosmid/BAC/YAC end sequences use Cosmid/Bacterial artificial chromosome/Yeast artificial chromosome to sequence the genome from the end side. These sequences act like very low copy plasmids that there is only one copy per cell sometimes. To get enough chromosome, they need a large number of E. coli culture that 2.5 - 5 litres may be a reasonable amount. Cosmid/BAC/YAC can also be used to get bigger clone of DNA fragment than vectors like plasmid and phagemid. A larger insert is often helpful for the sequence project in organizing clones. Eukaryotic proteins can be expressed by using YAC with posttranslational modification. BAC can’t do that, but BACs can reliably represent human DNA much better than YAC or cosmid. Exon trapped genomic sequences Exon trapped sequence is used to identify genes in cloned DNA, and this is achieved by recognizing and trapping carrier containing exon sequence of DNA. Exon trapping has two main features: First, it is independent of availability of the RNA expressing target DNA. Second, isolated sequences can be derived directly from clone without knowing tissues expressing the gene which needs to be identified. During slicing, exon can be remained in mRNA and information carried by exon can be contained in the protein. Since fragment of DNA can be inserted into sequences, if an exon is inserted into intron, the transcript will be longer than usual and this transcript can be trapped by analysis. Alu PCR sequences Alu repetitive element is member of Short Interspersed Elements (SINE) in mammalian genome. There are about 300 to 500 thousand copies of Alu repetitive element in human genome, which means one Alu element exists in 4 to 6 kb averagely. Alu elements are distributed widely in mammalian genome, and repeatability is one of the characteristics, that is why it is called Alu repetitive element. By using special Alu sequence as target locus, specific human DNA can be obtained from clone of TAC, BAC, PAC or human-mouse cell hybrid. PCR is an approach used to clone a small piece of fragment of DNA. The fragment could be one gene or just a part of gene. PCR can only clone very small fragment of DNA, which generally does not exceed 10kbp. Alu PCR is a "DNA fingerprinting" technique. This approach is rapid and easy to use. It is obtained from analysis