In the fist class, all copies have the same function, but the repetitive nature is probably to ensure that sufficient amounts of the gene product are produced. In the second class, the different copies of the gene can have separate, but related function, such as fetal hemoglobin vs. adult hemoglobin. These have either a tandem or dispersed organization. Telomeric sequences are an example. They perform a function in replication, because they serve as caps on the chromosomes, and due to a special mechanism of telomere replication, this prevents the shortening of the chromosome.
Several methods are available to identify the location of a gene within the genome.
Each cell line contains a subset of the human genome, so the presence of a human gene product in a subset of cell lines with the same human chromosome provides evidence for the location of the gene. Further linkage analysis with additional markers is used to further identify the position of the gene. High Resolution Genetic Maps Linkage analysis of human traits is accomplished by studying the transmission of the phenotype within pedigrees, and determining if there is an association with markers within the genome. This requires the availability of polymorphic genetic markers throughout the genome. The linkage relationship is then determined, and these can be used to identify the location of any new trait.