When a genome is first investigated, this map is nonexistent. The map improves with the scientific progress and is perfect when the genomic DNA sequencing of the species has been completed 642-145 exam. During this process, and for the investigation of differences in strain, the fragments are identified by small tags . These may be genetic markers (PCR products) or the unique sequence-dependent pattern of DNA-cutting enzymes. The ordering is derived from genetic observations (recombinant frequency) for these markers or in the second case from a computational integration of the fingerprinting data. The term "mapping" is used in two different but related contexts 70-294 exam.Two different ways of mapping are distinguished. Genetic mapping uses classical genetic techniques 70-536 exam (e.g. pedigree analysis or breeding experiments) to determine sequence features within a genome. Using modern molecular biology techniques for the same purpose is usually referred to as physical mapping.