caused by the strong promoter of the upstream fusion partner. The latter is common in lymphomas, where oncogenes are juxtaposed to the promoters of the immunoglobulin genes. Oncogenic fusion transcripts may also be caused by trans-splicing or read-through events. Since chromosomal translocations play such a significant role in neoplasia, a specialized database of chromosomal aberrations and gene fusions in cancer has been created. This database is called Mitelman Database of Chromosome Aberrations and Gene Fusions in Cancer. Diagnostics Presence of certain chromosomal aberrations and their resulting fusion genes is commonly used within cancer diagnostics in order to set a precise diagnosis. Chromosome banding analysis, fluorescence in situ hybridization (FISH), and reverse transcription polymerase chain reaction (RT-PCR) are common methods employed at diagnostic laboratories. These methods all have their distinct shortcomings due to the very complex nature of cancer genomes. Recent developments such as high-throughput sequencing and custom DNA microarrays bear promise of introduction of more efficient methods. Evolution Gene fusion plays a key role in the evolution of gene architecture. We can observe its effect if gene fusion occurs in coding sequences. Duplication, sequence divergence, and recombination are the major contributors at work in gene evolution. These events can probably produce new genes from already existing parts. When gene fusion happens in non-coding sequence region, it can lead to the misregulation of the expression of a gene now under the control of the cis-regulatory sequence of another gene. If it happens in coding sequences, gene fusion cause the assembly of a new gene, then it allows the appearance of new functions by adding peptide modules into multi domain protein. The detecting methods to inventory gene fusion events on a large biological scale can provide insights about the multi modular architecture of proteins. Purine biosynthesis The purines adenine and guanine are two of the four information encoding bases of the universal genetic code. Biosynthesis of these purines occurs by similar, but not identical, pathways in different species of the three domains of life, the Archaea, Bacteria and Eukaryotes. A major distinctive feature of the purine biosynthetic pathways in Bacteria is the prevalence of gene fusions where two or more purine biosynthetic enzymes are encoded by a single gene. Such gene fusions are almost exclusively between genes that encode enzymes that perform sequential steps in the biosynthetic pathway. Eukaryotic species generally exhibit the most common gene fusions seen in the Bacteria, but