Polytene Chromosomes as a Genotoxicology Tool

It is not possible to visualize the interphase chromosomes with light microscopy; however, polytene chromosomes are giant interphase chromosomes visible under light microscopy. Therefore, polytene chromosomes of Drosophila melanogaster are unique materials for the observation and analysis of the genome and genetic organization of chromosomes in the interphase stage. Polytene chromosomes form through the sequential replication of the chromosomes of the diploid nucleus division of the cytoplasm following the replication. This way, a chromosome 70 to 110 time thicker than a typical metaphase chromosome and observable with light microscopy, appears. This interesting polyteny occurs within the cellular cycle, during the mid-phases of Drosophila melanogaster's embryogenesis under ecdysone, which is particularly important for the development of larva. Investigation of every aspect of polytene chromosomes is very useful for the analysis of chromosomal organization and genome as a whole.