You Have Used a Variation of Fluorescence in Situ Hybridization

Short Answer

You have used a variation of fluorescence in situ hybridization (FISH) called flow-FISH. In this technique, DNA probes are labeled with fluorescence and hybridized to their targets inside the cells in a tissue. The cells are then sorted using a fluorescence-activated cell sorter based on their fluorescent signal intensity. The probes in your experiment are designed to hybridize to human telomeric sequences at the ends of the chromosomes. You perform flow-FISH using these probes on two human cell types, an early primary fibroblast culture and a late secondary culture that is showing the signs of replicative cell senescence. The sorting results are presented in the following histograms. Which histogram (1 or 2) would you expect to correspond to the primary culture?